Tabs in recipe book and Creative inventory do not support translucent pixels

More loosely relates to these issues: MC-144009 MC-145821 MC-164001 MC-165403

The bug

If the textures used for the tabs in the Creative inventory or recipe book contain translucent pixels, these will be rendered completely opaque in-game.

Images attached to MC-109447 show that this was not previously the case (aside from a bug where the first tab of each would always be opaque).

Tabs in the advancement screen are not affected by this issue, and correctly render as transparent at all times.

How to reproduce

1. Download and apply the attached resource pack

2. Enter the Creative inventory or recipe book

3. Observe

Expected results

Translucent tabs.

Actual results

Entirely opaque.