fix: send change events always

[rainest]

Summary

Fixes a bug in the event sender. The original structure of this section meant that GDR only sent change events to the channel if they had encountered in an error. This did not make the KIC DB mode error event generator unhappy, but did not work very well for Kong/kubernetes-ingress-controller#6131, as it did not see most change events. Whoops.

This assigns the error to the event regardless of whether it's nil or not (it'll either populate or just remain nil) and sends the event off before checking for a non-nil error and performing the error return.

After this change, the channel will receive successful events also. This was the original intent, but the breakage went unnoticed til I tried to actual look at successful events.

[codecov-commenter]

Codecov Report

Attention: Patch coverage is 0% with 10 lines in your changes missing coverage. Please review.

Project coverage is 41.35%. Comparing base (61fbc91) to head (96cece3).

Files	Patch %	Lines
pkg/diff/diff.go	0.00%	10 Missing ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##             main     #119      +/-   ##
==========================================
- Coverage   41.35%   41.35%   -0.01%     
==========================================
  Files          75       75              
  Lines       10895    10896       +1     
==========================================
  Hits         4506     4506              
- Misses       5925     5926       +1     
  Partials      464      464              

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