[Bf-blender-cvs] [78c7e7e3bc2] blender-v2.83-release: Fix T78337: Fix crash when use GPencil merge without materials

[Antonio Vazquez]

Commit: 78c7e7e3bc26896aae0334362ab91a9025e22a7d
Author: Antonio Vazquez
Date:   Sat Jun 27 15:58:45 2020 +0200
Branches: blender-v2.83-release
https://developer.blender.org/rB78c7e7e3bc26896aae0334362ab91a9025e22a7d

Fix T78337: Fix crash when use GPencil merge without materials

If the object hadn't material, the index of material was negative.

===================================================================

M	source/blender/editors/gpencil/gpencil_merge.c

===================================================================

diff --git a/source/blender/editors/gpencil/gpencil_merge.c b/source/blender/editors/gpencil/gpencil_merge.c
index e71bf2098dd..6417d31d894 100644
--- a/source/blender/editors/gpencil/gpencil_merge.c
+++ b/source/blender/editors/gpencil/gpencil_merge.c
@@ -132,7 +132,7 @@ static bGPDstroke *gpencil_prepare_stroke(bContext *C, wmOperator *op, int totpo
   bGPDframe *gpf = BKE_gpencil_layer_frame_get(gpl, CFRA, add_frame_mode);
 
   /* stroke */
-  bGPDstroke *gps = BKE_gpencil_stroke_new(ob->actcol - 1, totpoints, brush->size);
+  bGPDstroke *gps = BKE_gpencil_stroke_new(max(ob->actcol - 1, 0), totpoints, brush->size);
   gps->flag |= GP_STROKE_SELECT;
 
   if (cyclic) {