I have converted our DB v13 to v14 via odoo upgrade. but when I try with upgrade database it is give error about scss related. Here I post of that.

Undefined variable: "$ o-mail-thread-window-zindex".
on line 14123 of stdin
>> z-index: $ o-mail-thread-window-zindex + 1;

------------- ^
This error occured while compiling the bundle 'web.assets_backend' containing:
- /web/static/lib/bootstrap/scss/_functions.scss
- / web / static / lib /bootstrap/scss/_mixins.scss
- /web/static/src/scss/bs_mixins_overrides.scss
- /web/static/src/scss/utils.scss
-
/web/static/src/scss/primary_variables.scssiables. scss - /static/src/scss/primary_variables.scss
- /web_editor/static/src/scss/web_editor.variables.scss
-
/ web_editor / static / src / scss / 13_0_color_system_support_primary_variables. scss
- /portal/static/src/scss/primary_variables.scss
- /account/static/src/scss/variables.scss
- /marketing_automation/static/src/scss/variables.scss
- /hr_org_chart/static/src/scss/variables.scss
- /web_editor/static/src/scss/secondary_variables.scss
- / web_enterprise / static / / src / scss / secondary_variables / static / src / scss .scss
- /web/static/src/scss/secondary_variables.scss
- /web_editor/static/src/scss/bootstrap_overridden_backend.scss
- /web_editor/static/src/scss/bootstrapenterprise_overridden.scss
/ srcprise_overridden.scss/ /bootstrap_overridden.scss
- /web/static/lib/bootstrap/scss/_variables.scss
- /web/static/src/scss/import_bootstrap.scss
-
/web/static/src/scss/bootstrap_review.scss / static /src/scss/webclient.scss
- /web_enterprise/static/src/scss/webclient_layout.scss
- /web/static/src/scss/webclient.scss
- /web/static/src/scss/domain_selector.scss
- / web / static / src / scss / model_field_selector .scss
- /web/static/src/scss/progress_bar.scss
- /web/static/src/scss/dropdown.scss
- /web_enterprise/static/src/scss/dropdown.scss
- / web / static / src / scss /tooltip.scss
- /web/static/src/scss/switch_company_menu.scss
- /web/static/src/scss/debug_manager.scss
- /web/static/src/scss/control_panel.scss
- / web / static / src /scss/fields.scss
- /web_enterprise/static/src/scss/fields.scss
- /web/static/src/scss/views.scss
- /web/static/src/scss/pivot_view.scss
- /web/static/src/scss/graph_view.scss
- /web/static/src/scss/form_view.scss
- / web_enterprise / static / src / scss / form_view .scss
- /web/static/src/scss/list_view.scss
- /web_enterprise/static/src/scss/list_view.scss
- /web/static/src/scss/kanban_dashboard.scss
- / web / static / src / scss /kanban_examples_dialog.scss
- /web/static/src/scss/kanban_column_progressbar.scss
- /web/static/src/scss/kanban_view.scss
- /web/static/src/scss/kanban_view_mobile.scss
/ src - / web /scss/web_calendar.scss
- /web/static/src/scss/web_calendar_mobile.scss
- /web/static/src/scss/search_view.scss
- /web/static/src/scss/search_panel.scss
- /web/static/src/scss/search_view_mobile.scss
- /web/static/src/scss/dropdown_menu.scss
- / web_enterprise / static / src / scss / search_view .scss
- /web/static/src/scss/data_export.scss
- /base/static/src/scss/onboarding.scss
- /web/static/src/scss/attachment_preview.scss
- / web / static / src / scss /notification.scss
- /web/static/src/scss/base_document_layout.scss
- /web/static/src/scss/ribbon.scss
- /web/static/src/scss/base_settings.scss
- / web / static / src /scss/report_backend.scss
- /web_mobile/static/src/scss/mobile.scss
- /web_mobile/static/src/scss/pivot_view_mobile.scss
- /web_grid/static/src/scss/grid_view.scss
- /web_editor/static/src/scss/web_editor.common.scss
- /web_editor/static/src/scss/web_editor.backend.scss
- / sr_enterprise / static. /scss/home_menu.scss
- /web_enterprise/static/src/scss/home_menu_layout.scss
-
/web_enterprise/static/src/scss/search_panel_mobile.scss
- /web_enterprise/static/srcss/scss_senterprise/static/srcss/scss_menuprise/static/srcss/scss_menuprise/static/srcss/scss_menuprise/ /src/scss/menu_search.scss
- /web_enterprise/static/src/scss/control_panel_layout.scss
- /web_enterprise/static/src/scss/datepicker.scss
- /web_enterprise/static/src/scss/kanban_view.scss
- / web_enterprise /static/src/scss/touch_device.scss
- /web_enterprise/static/src/scss/snackbar.scss
- /web_enterprise/static/src/scss/swipe_item_mixin.scss
- /web_enterprise/static/src/scss/form_view_mobile.scssview
- / sranbancprise / static_mobile.scssview - / sranbancprise / scobile.scssview - / sranbancprise / static_mobile.scssview .scss
- /web_enterprise/static/src/scss/modal_mobile.scss
- /web/static/src/scss/navbar_mobile.scss
- /web_gantt/static/src/scss/web_gantt.scss
- / base_import / static / src /base_import.scss
- /mail/static/src/scss/announcement.scss
- /mail/static/src/scss/discuss.scss
- /mail/static/src/scss/abstract_thread_window.scss
- / mail / static / src /scss/thread_window.scss
- /mail/static/src/scss/composer.scss
- /mail/static/src/scss/chatter.scss
- /mail/static/src/scss/followers.scss
- /mail/static/src/scss/thread.scss
- / mail / static / src / scss / systray .scss
- /mail/static/src/scss/mail_activity.scss
- /mail/static/src/scss/activity_view.scss
- /mail/static/src/scss/kanban_view.scss
- / mail / static / src / scss /attachment_box.scss
- /account/static/src/scss/account_reconciliation.scss
- /account/static/src/scss/account_journal_dashboard.scss
- /account/static/src/scss/account_dashboard.scss
/ account / static_dashboard.scss - / /scss/account_searchpanel.scss
- /account/static/src/scss/section_and_note_backend.scss
- /account/static/src/scss/account_activity.scss
- /account_accountant/static/src/scss/move_line_list_view.scss
- /account_reports/static/src/scss/account_financial_report.scss
- / account_online_sync / static_scss - / account_online_sync / static_scss / account_online_sync / static_scss .scss
- /calendar/static/src/scss/calendar.scss
- /sales_team/static/src/scss/sales_team_dashboard.scss
- /point_of_sale/static/src/scss/pos_dashboard.scss
- / website / static / src / scss /website.backend.scss
- /website/static/src/scss/website_visitor_views.scss
- /website_livechat/static/src/scss/mail_thread_visitor_info.scss
- /hr/static/src/scss/hr.scss
- / static /src/scss/note.scss
- /account_asset/static/src/scss/account_asset.scss
- /mass_mailing/static/src/scss/mass_mailing.scss
- /mass_mailing/static/src/scss/mass_mailing_mobile.scss
- / gamification / / static / srcification .scss
- /website_crm_score/static/src/scss/website_crm_score.scss
- /project/static/src/scss/project_dashboard.scss
- /voip/static/src/scss/call_center_field.scss
/ src /voip.scss
- /website_sale/static/src/scss/website_sale_dashboard.scss
- /website_sale/static/src/scss/website_sale_backend.scss - /event/static/src/scss/
event_scchat
- / imevent.scchat /scss/im_livechat_history.scss
- /im_livechat/static/src/scss/im_livechat_form.scss
- /stock_barcode/static/src/scss/stock_barcode.scss
- /stock_barcode/static/src/scss/client_action.scss
- / stock_barcode / src_mobile_static / scsscode / srcode_cmobile / static code .scss
- /helpdesk/static/src/scss/helpdesk.scss
- /stock/static/src/scss/stock_traceability_report.scss
- /marketing_automation/static/src/scss/marketing_automation.scss
- / sr_css / static / scss / timesheet / timesheet / /sale_timesheet.scss
- /web_cohort/static/src/scss/web_cohort.scss
- /web_dashboard/static/src/scss/dashboard_view.scss
- /mail_enterprise/static/src/scss/mail_enterprise.scss / static / mail_enterprise.scss
- / mail_enterprise / srcenter /scss/mail_enterprise_mobile.scss
- /sale/static/src/scss/sale_onboarding.scss
- /sale/static/src/scss/product_configurator.scss
- /account_invoice_extract/static/src/scss/account_invoice_extract.scss
- / sms / static / src .scss
- /partner_autocomplete/static/src/scss/partner_autocomplete.scss
- /snailmail/static/src/bugfix/bugfix.scss - /
snailmail
/static/src/ components / snailmail static_notification_popover / spovermail_ notification survey_popover / spovermail_notification survey_popover / spovermail_notification / survey src /scss/survey_views.scss
- /sale_enterprise/static/src/scss/sale_enterprise.scss
- /base_setup/static/src/scss/settings.scss
- /resource/static/src/scss/section_backend.scss - / utm / static_backend.scss -
/src/scss/utm_views.scss
- /web_map/static/src/scss/mapview.scss
- /hr_contract/static/src/scss/state_selection.scss
- /hr_contract/static/src/scss/calendar_mismatch.scss
- / planning / static / src / scsser / field_colorpick .scss
- /stock_enterprise/static/src/scss/report_stock_quantity.scss
- /payment/static/src/scss/payment_acquirer.scss
- /account_reports/static/src/scss/account_financial_report.scss_
/ hr_org_financial_report.scss_chart / scssc / hr_org_port. /hr_org_chart.scss
- /social/static/src/scss/social.scss
- /social_facebook/static/src/scss/social_facebook.scss
- /social_linkedin/static/src/scss/social_linkedin.scss
- / social_twitter /scss/social_twitter.scss
- /social_push_notifications/static/src/scss/social_push_notifications.scss - /gws_google_maps/static/src/scss/web_maps.scss
- /gws_google_maps/static/src/scss_notifications.scss
- /gws_google_maps/static/src/scss/web_maps.scss
- /gws_google_maps/static/src/scss/web_maps_mobile / srcssalis / scssapprapprais / hscssalis / hscssrapprais / hscssal .scss
- /purchase/static/src/scss/purchase.scss
- /timer/static/src/scss/timer_button.scss
- /project_timesheet_forecast/static/src/scss/forecast_gantt.scss

I have a check that libsaas lib is installed on our server and we used odoo.sh for that.