Update jobs_current_version_uuid_index and jobs_symlink_target_uuid_index to ignore NULL values

[collado-mike]

Problem

Most jobs don't have a symlink target and jobs don't have a current version until they've had at least one successful run. The indices recently added will always write to the index, even when the indexed values are null.

Solution

Avoid writing to the indices when indexed values are null

Checklist

• You've signed-off your work
• Your changes are accompanied by tests (if relevant)
• Your change contains a small diff and is self-contained
• You've updated any relevant documentation (if relevant)
• You've updated the CHANGELOG.md with details about your change under the "Unreleased" section (if relevant, depending on the change, this may not be necessary)
• You've versioned your .sql database schema migration according to Flyway's naming convention (if relevant)
• You've included a header in any source code files (if relevant)

[phixMe]

Thanks

[codecov]

Codecov Report

Merging #2186 (c581ebc) into main (a458374) will not change coverage.
The diff coverage is n/a.

@@            Coverage Diff            @@
##               main    #2186   +/-   ##
=========================================
  Coverage     76.60%   76.60%           
  Complexity     1136     1136           
=========================================
  Files           219      219           
  Lines          5287     5287           
  Branches        420      420           
=========================================
  Hits           4050     4050           
  Misses          765      765           
  Partials        472      472           

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