Hello,

I get this error when I enter a menu that I created. I can't find documentation about it, does anyone know how to solve it?

  File "/opt/odoo/odoo-server/odoo/addons/base/models/ir_ui_view.py", line 2445, in <dictcomp>
    v_type: self.get_view(
  File "/opt/odoo/odoo-server/odoo/addons/base/models/ir_ui_view.py", line 2630, in get_view
    result = dict(self._get_view_cache(view_id, view_type, **options))
  File "/opt/odoo/odoo-server/odoo/addons/base/models/ir_ui_view.py", line 2586, in _get_view_cache
    arch, view = self._get_view(view_id, view_type, **options)
  File "/opt/odoo/odoo-server/odoo/addons/base/models/ir_ui_view.py", line 2533, in _get_view
    arch = view._get_combined_arch()
  File "/opt/odoo/odoo-server/odoo/addons/base/models/ir_ui_view.py", line 950, in _get_combined_arch
    arch = root.with_prefetch(tree_views._prefetch_ids)._combine(hierarchy)
  File "/opt/odoo/odoo-server/odoo/addons/base/models/ir_ui_view.py", line 868, in _combine
    combined_arch = etree.fromstring(self.arch)
  File "src/lxml/etree.pyx", line 3252, in lxml.etree.fromstring
  File "src/lxml/parser.pxi", line 1912, in lxml.etree._parseMemoryDocument
ValueError: can only parse strings

The above server error caused the following client error:
OwlError: An error occured in the owl lifecycle (see this Error's "cause" property)
    Error: An error occured in the owl lifecycle (see this Error's "cause" property)
        at handleError (http://javierdiez:8069/web/assets/2c356e4/web.assets_web.min.js:916:101)
        at App.handleError (http://javierdiez:8069/web/assets/2c356e4/web.assets_web.min.js:1545:29)
        at ComponentNode.initiateRender (http://javierdiez:8069/web/assets/2c356e4/web.assets_web.min.js:1006:19)

Caused by: RPC_ERROR: Odoo Server Error
    RPC_ERROR