Steps to reproduce:
1. Download and open the attached project
2. Observe scene or game view

Expected behavior: all cubes bake the same emission
Actual behavior: middle cube, with shader pragma set to "alpha:fade" or "alpha:premul" does not bake emission

Reproduced on: 5.4.3f1, 5.4.3p3, 5.5.0p3, 5.6.0b1
Unable to test on 5.3- due to the shader breaking

Notes:
-user notes that the third cube is "fixed" by removing the colormask entry in the shader's code