[MaterialEditor] Vestigial alpha_a and alpha_b sliders bug

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Not entirely sure if this is intended:

The main_skin shader, if duplicated ('copy material'), will expose the alpha_a and alpha_b sliders on the duplicated copy, by default set to 0.

Adding an AlphaMask texture to the second material will fail to work as a result/the alphamask is ignored and no transparency is applied.

This is usually not an issue because you can just set those sliders to 1 to get the expected effect, but if you'd already changed to a different shader, those sliders are hidden but retain their 0 value, and so it isn't immediately obvious why AlphaMasking fails to do anything.

I read in the changelog that alpha_a and alpha_b sliders were removed a while back, so what would be the best way to solve this (obscure) issue? Or would trying to do so cause too many problems with clothing tops?