Pneumatic helmet HUD is leaving OpenGL state wrong, causing active item in hotbar to render with opaque background (and occasional opaque flicker in chat window). Need to track down exactly what & where (something to do with animated panel rendering, possibly?)

Note 1: Opaque background only occurs when no block is highlighted, so the block highlighting code does appear to reset the state.

Note 2: Commenting out entity tracker rendering (https://github.com/desht/pnc-repressurized/blob/master/src/main/java/me/desht/pneumaticcraft/client/render/pneumaticArmor/EntityTrackUpgradeHandler.java#L171) didn't make a difference. Interesting.