Blender Git Loki

Fix T41349: Muting texture nodes can cause crashes.

Problem is that setup of stack indices which refer to the same stack
entry can lead to cyclic TexDelegate node pointers, causing an infinite
loop.

Fixing this would take too much time and require recoding large parts of
the texnodes system, which is earmarked for scrapping anyway ... So for
now just disabled muting in texnodes to avoid crashes.