Fixes two bugs: one with correctly setting and preserving channel enabled state, and the other with correctly setting the mask channel.
If no mask channel is set (testing for values < 0) then use mask_alpha = 1. This currently assumes that mask channel will not be set more than once during the lifetime of the volume. (You either have a mask channel or you don't)
Fixes two bugs: one with correctly setting and preserving channel enabled state, and the other with correctly setting the mask channel.
If no mask channel is set (testing for values < 0) then use mask_alpha = 1. This currently assumes that mask channel will not be set more than once during the lifetime of the volume. (You either have a mask channel or you don't)