Reset splitter sizes on database unlock

[droidmonkey]

• Attempt to avoid issue with splitters not being appropriately calculated because the main window isn't sized yet. This can happen if the main window is hidden when the database is loaded and the splitter sizes are not recorded in the config file.
• Fixes #11013

Testing strategy

Manual testing is pending...

Type of change

• ✅ Bug fix (non-breaking change that fixes an issue)

[codecov[bot]]

Codecov Report

All modified and coverable lines are covered by tests :white_check_mark:

Project coverage is 63.74%. Comparing base (166a371) to head (ac96b79).

Additional details and impacted files

```diff @@ Coverage Diff @@ ## develop #11014 +/- ## =========================================== - Coverage 63.77% 63.74% -0.03% =========================================== Files 362 362 Lines 44755 44759 +4 =========================================== - Hits 28542 28529 -13 - Misses 16213 16230 +17 ```

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