fix logic for setting alternate background in mod list items

[grahamlangford]

What does this PR do?

• Fixes bug with the logic to set the alternate background in ModListItem

Demo

• 

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[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 75.76%. Comparing base (8318d74) to head (afee199).
Report is 513 commits behind head on main.

Additional details and impacted files

@@            Coverage Diff             @@
##             main    #9528      +/-   ##
==========================================
+ Coverage   74.24%   75.76%   +1.52%     
==========================================
  Files        1332     1427      +95     
  Lines       40817    43058    +2241     
  Branches     7634     7924     +290     
==========================================
+ Hits        30306    32625    +2319     
+ Misses      10511    10433      -78     

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Playwright test results

 152 passed
 2 flaky
 2 skipped

Details

 Open report ↗︎
 156 tests across 51 suites
 11 minutes, 13 seconds
 afee199
 For more information on how to debug and view this report, see our readme

Flaky tests

msedge › tests/extensionConsole/activation.spec.ts › can activate a mod via url
chrome › tests/pageEditor/saveMod.spec.ts › shows error notification when updating a public mod without incrementing the version

Skipped tests

chrome › tests/runtime/googleSheetsIntegration.spec.ts › can activate a google spreadsheet mod with config options
msedge › tests/runtime/googleSheetsIntegration.spec.ts › can activate a google spreadsheet mod with config options