Fixed a small bug in new gear library/gear metadata presets, which resulted in the values for the first selected gear preset did not get displayed when opening manage->gear presets

[jboneng]

Summary

Fixes gear preset camera/lens/film combos showing — None — when first opening Manage… → Gear Presets.

Switching categories triggered _populate_form() (which set the correct combo values) and then an extra _refresh_preset_combos() that cleared the combos without re-applying the preset’s IDs.

Test plan

• Open Manage… → Gear Presets — first preset shows linked camera, lens, and film stock
• Switch between presets — selections stay correct
• Switch to Cameras/Lenses/Film Stocks and back — preset combos still populate correctly