Right-clicking non-interactive blocks with a helmet in your hand results in Minecraft crashing. This happens with all helmets and in all game modes. In addition, right clicking with other pieces of armor causes them to go one slot above where they should go.
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Confirmed.

Although this problem appeared to be due not to using on blocks, but in general due to the assigning slots being offset. Chest, Legs, and Shoes would all mount one slot higher than the last, meaning the Helmet was likely offset tn a completely invalid slot which cases the game to crash upon attempt. But at least this is fixed now. 🙂