fixed flawed icon optimization.

Using Imagemagick:
convert -strip -size 128x128 xc:"rgba(0,0,0,0)" PNG32:blank.png
convert -strip -size 128x128 xc:"rgba(0,0,0,0)" PNG32:colorother.png
convert -strip -size 128x128 xc:"rgba(0,0,0,0)" PNG32:donothing.png