[BUG] Maintenance tasks can no longer be edited

[biselx]

Describe the bug
When I modify a maintenance task, I get an internal server error.

To Reproduce
Steps to reproduce the behavior:

1. Go to 'Maintenance tasks'
2. Click on 'Active'
3. Click on 'Description Task'
4. Click on 'Edit'
5. See error

Tracebacks

Traceback (most recent call last):
  File "/opt/venvs/nav/lib/python3.7/site-packages/django/core/handlers/exception.py", line 47, in inner
    response = get_response(request)
  File "/opt/venvs/nav/lib/python3.7/site-packages/django/core/handlers/base.py", line 181, in _get_response
    response = wrapped_callback(request, *callback_args, **callback_kwargs)
  File "/usr/lib/python3.7/contextlib.py", line 74, in inner
    return func(*args, **kwds)
  File "/opt/venvs/nav/lib/python3.7/site-packages/nav/web/maintenance/views.py", line 288, in edit
    if component_keys_errors:
UnboundLocalError: local variable 'component_keys_errors' referenced before assignment

Environment (please complete the following information):

• If the problem is with the web ui: Linux or Windows, Firefox or Brave
• OS on the NAV server : Debian 10
• NAV version installed 5.8.3
• Method of installation from Debian package

[lunkwill42]

Thanks for the bug report! Easily reproduced on my end.

I assume this may be a regression error due to the changes in #2757, but I'll have a closer look.

[lunkwill42]

Fixed by #2784