Fix mirv_streams crashbug
Fix mirv_streams crashbug

- Fixed mirv_streams crashbug that e.g. could happen on listen servers when CS:GO was freeing a material (e.g. when POV player died) on the drawing thread while in the view rendering functions on the drawing thread at same time, causing HLAE to crash (tried to lock a mutex twice from same thread).

ripieces/advancedfx,ripieces/advancedfx,ripieces/advancedfx,ripieces/advancedfx