4.14 Crash in FMetalRHICommandContext::RHISetShaderUniformBuffer when opening material editor with forward rendering enabled on mac

Just ran into this. The material editor will constantly crash if you create a scalar parameter and try to expand it.

As a workaround, disabling forward rendering in project settings fixes the crash.

Presumably the forward path hasn’t been tested much on mac hardware as it is primarily intended for VR, which has limited support on the mac at the moment.