Traceback (most recent call last):

  File "/home/ubuntu/mahesh/odoo_playground/odoo/service/server.py", line 1198, in preload_registries

    registry = Registry.new(dbname, update_module=update_module)

  File "/home/ubuntu/mahesh/odoo_playground/odoo/modules/registry.py", line 89, in new

    odoo.modules.load_modules(registry._db, force_demo, status, update_module)

  File "/home/ubuntu/mahesh/odoo_playground/odoo/modules/loading.py", line 497, in load_modules

    env['ir.model.data']._process_end(processed_modules)

  File "/home/ubuntu/mahesh/odoo_playground/odoo/addons/base/models/ir_model.py", line 2235, in _process_end

    record.unlink()

  File "/home/ubuntu/mahesh/odoo_playground/odoo/addons/base/models/ir_model.py", line 1357, in unlink

    self._process_ondelet()

  File "/home/ubuntu/mahesh/odoo_playground/odoo/addons/base/models/ir_model.py", line 1382, in _process_ondelete

    ondelete = (field.ondelete or {}).get(selection.value) or 'set null'

AttributeError: 'str' object has no attribute 'get'