Issue with direct gui image transparency

[fireclawthefox]

If simplepbr is enabled, images put on direct gui elements that have set their transparency to either M_multisample or M_multisample_mask will not be shown as transparent anymore. Other transparency types do work. This also only applies to images, the frame color for example shows correctly transparent.

I've attached files that displays the behavior for all available transparency types:
transparency sample.zip