title: web.assets_backend external id not found in odoo 15
body: <p>when i tried inherit external id web.assets_backend odoo says that external id not found
  here's the error log:</p>
  <pre><code>Traceback (most recent call last):
    File &quot;/opt/odoo/sources/odoo/odoo/tools/cache.py&quot;, line 85, in lookup
      r = d[key]
    File &quot;/opt/odoo/sources/odoo/odoo/tools/func.py&quot;, line 71, in wrapper
      return func(self, *args, **kwargs)
    File &quot;/opt/odoo/sources/odoo/odoo/tools/lru.py&quot;, line 34, in __getitem__
      a = self.d[obj]
  KeyError: ('ir.model.data', &lt;function IrModelData._xmlid_lookup at 0x7fb3865beaf0&gt;, 'web.assets_backend')
  
  During handling of the above exception, another exception occurred:
  
  Traceback (most recent call last):
    File &quot;/opt/odoo/sources/odoo/odoo/tools/convert.py&quot;, line 680, in _tag_root
      f(rec)
    File &quot;/opt/odoo/sources/odoo/odoo/tools/convert.py&quot;, line 658, in _tag_template
      return self._tag_record(record)
    File &quot;/opt/odoo/sources/odoo/odoo/tools/convert.py&quot;, line 567, in _tag_record
      f_val = self.id_get(f_ref)
    File &quot;/opt/odoo/sources/odoo/odoo/tools/convert.py&quot;, line 663, in id_get
      res = self.model_id_get(id_str, raise_if_not_found)
    File &quot;/opt/odoo/sources/odoo/odoo/tools/convert.py&quot;, line 669, in model_id_get
      return self.env['ir.model.data']._xmlid_to_res_model_res_id(id_str, raise_if_not_found=raise_if_not_found)
    File &quot;/opt/odoo/sources/odoo/odoo/addons/base/models/ir_model.py&quot;, line 1935, in _xmlid_to_res_model_res_id
      return self._xmlid_lookup(xmlid)[1:3]
    File &quot;&lt;decorator-gen-35&gt;&quot;, line 2, in _xmlid_lookup
    File &quot;/opt/odoo/sources/odoo/odoo/tools/cache.py&quot;, line 90, in lookup
      value = d[key] = self.method(*args, **kwargs)
    File &quot;/opt/odoo/sources/odoo/odoo/addons/base/models/ir_model.py&quot;, line 1928, in _xmlid_lookup
      raise ValueError('External ID not found in the system: %s' % xmlid)
  ValueError: External ID not found in the system: web.assets_backend
  </code></pre>
  <p>what is the solution for this issue?
  thanks in advance</p>