Fix #31743: Applying Smooth modifier to a curve crashes Blender

Actually there were two different issues involved here:

- Recently enabled Smooth modifier wasn't actually designed for curves, so
  it in fact requires a bit bigger work to make it working.

  For now added check for object's typy in this modifier and if it's not
  mesh, it wouldn't try to use edges.

  The reason why it worked in 3d viewport is that creating DM from curve while
  displist is still ocntrcuting for would result in empty CDDM and that leads to
  not taking edges into account, only vertexCos passed to modifier would be used.

  This makes it behaving a bit differently from if it was a mesh, but still gives
  quite reasonable result. Would leave actual fix for a guy who enabled smooth
  modifier.

- Another issue is related on ensuring sculpt mask layer after applying modifier.
  This shall happen only for meshes.

2 files changed, 12 insertions, 4 deletions

diff --git a/source/blender/editors/object/object_modifier.c b/source/blender/editors/object/object_modifier.c
index 7dd17e59f6f..d6b5fb9fc10 100644
--- a/source/blender/editors/object/object_modifier.c
+++ b/source/blender/editors/object/object_modifier.c
@@ -642,8 +642,10 @@ int ED_object_modifier_apply(ReportList *reports, Scene *scene, Object *ob, Modi
 	BLI_remlink(&ob->modifiers, md);
 	modifier_free(md);
 
-	/* ensure mesh paint mask layer remains after applying */
-	ED_sculpt_mask_layers_ensure(ob, NULL);
+	if (ob->type == OB_MESH) {
+		/* ensure mesh paint mask layer remains after applying */
+		ED_sculpt_mask_layers_ensure(ob, NULL);
+	}
 
 	return 1;
 }
diff --git a/source/blender/modifiers/intern/MOD_smooth.c b/source/blender/modifiers/intern/MOD_smooth.c
index 1313f5aa3ef..7b230d7365d 100644
--- a/source/blender/modifiers/intern/MOD_smooth.c
+++ b/source/blender/modifiers/intern/MOD_smooth.c
@@ -118,8 +118,14 @@ static void smoothModifier_do(
 	fac = smd->fac;
 	facm = 1 - fac;
 
-	medges = dm->getEdgeArray(dm);
-	numDMEdges = dm->getNumEdges(dm);
+	if (ob->type == OB_MESH) {
+		medges = dm->getEdgeArray(dm);
+		numDMEdges = dm->getNumEdges(dm);
+	}
+	else {
+		medges = NULL;
+		numDMEdges = 0;
+	}
 
 	modifier_get_vgroup(ob, dm, smd->defgrp_name, &dvert, &defgrp_index);