Fix a crasher in WeightVG modifiers.

Problem was, if no vertices were ever added to one of the obect's vgroups, there is no CD_DEFORMVERT layer, even though there might be several valid vgroup indices... Odd no one noticed that earlier.

Many thanks to miikah for finding that bug!

1 files changed, 11 insertions, 0 deletions

diff --git a/source/blender/modifiers/intern/MOD_weightvgedit.c b/source/blender/modifiers/intern/MOD_weightvgedit.c
index bdd7ab7486b..e090ad78e59 100644
--- a/source/blender/modifiers/intern/MOD_weightvgedit.c
+++ b/source/blender/modifiers/intern/MOD_weightvgedit.c
@@ -204,6 +204,17 @@ static DerivedMesh *applyModifier(ModifierData *md, Object *ob, DerivedMesh *der
 		return dm;
 
 	dvert = CustomData_duplicate_referenced_layer(&dm->vertData, CD_MDEFORMVERT, numVerts);
+	/* If no vertices were ever added to an object's vgroup, dvert might be NULL. */
+	if(!dvert)
+		/* If this modifier is not allowed to add vertices, just return. */
+		if(!do_add)
+			return dm;
+		/* Else, add a valid data layer! */
+		dvert = CustomData_add_layer_named(&dm->vertData, CD_MDEFORMVERT, CD_CALLOC,
+		                                   NULL, numVerts, wmd->defgrp_name);
+		/* Ultimate security check. */
+		if(!dvert)
+			return dm;
 
 	/* Get org weights, assuming 0.0 for vertices not in given vgroup. */
 	org_w = MEM_mallocN(sizeof(float) * numVerts, "WeightVGEdit Modifier, org_w");