Fixing django-polymorphic admin integration raises KeyError 'available_apps'

[kygoh]

When adding model that inherits from django-polymorphic PolymorphicModel in admin, the following error is thrown:

  File "/home/ubuntu/managedprojects/env/lib/python3.8/site-packages/django_adminlte_theme/templatetags/admin_menu.py", line 159, in menu_tag
    return Menu.admin_apps(context, Menu.render(context))
  File "/home/ubuntu/managedprojects/env/lib/python3.8/site-packages/django_adminlte_theme/templatetags/admin_menu.py", line 103, in admin_apps
    for app in context['available_apps']:
  File "/home/ubuntu/managedprojects/env/lib/python3.8/site-packages/django/template/context.py", line 83, in __getitem__
    raise KeyError(key)
KeyError: 'available_apps'

[quevon24]

Please accept this merge request, this error also happens with django-adminlte2