fix(KFLUXBUGS-1754): rp shouldn't show matched if RPA doesn't exist

[johnbieren]

This commit fixes the loader function to return nil instead of an empty RPA if the RPA specified in the RP label does not exist.

[codecov[bot]]

Codecov Report

Attention: Patch coverage is 80.00000% with 1 line in your changes missing coverage. Please review.

Project coverage is 82.40%. Comparing base (aade749) to head (5486574). Report is 5 commits behind head on main.

Files with missing lines	Patch %	Lines
loader/loader.go	80.00%	1 Missing :warning:

Additional details and impacted files

```diff @@ Coverage Diff @@ ## main #590 +/- ## ========================================== - Coverage 84.21% 82.40% -1.81% ========================================== Files 26 26 Lines 1742 2103 +361 ========================================== + Hits 1467 1733 +266 - Misses 191 286 +95 Partials 84 84 ```

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[happybhati]

/retest

[johnbieren]

/retest

[openshift-ci[bot]]

New changes are detected. LGTM label has been removed.

[johnbieren]

/retest

[johnbieren]

/retest