Fix T96494: Array modifier with caps crash on curve objects

Since 3b6ee8ce, a list of vertex groups cannot be retrieved
from curve objects for merging because curve objects do not support
vertex groups. Previously the empty list on the object was returned.
Only mesh objects are supported for the caps.

source/blender/modifiers/intern/MOD_array.c

@@ -412,8 +412,10 @@ static Mesh *arrayModifier_doArray(ArrayModifierData *amd,
 
   Object *start_cap_ob = amd->start_cap;
   if (start_cap_ob && start_cap_ob != ctx->object) {
+    if (start_cap_ob->type == OB_MESH && ctx->object->type == OB_MESH) {
       vgroup_start_cap_remap = BKE_object_defgroup_index_map_create(
           start_cap_ob, ctx->object, &vgroup_start_cap_remap_len);
+    }
 
     start_cap_mesh = BKE_modifier_get_evaluated_mesh_from_evaluated_object(start_cap_ob, false);
     if (start_cap_mesh) {
@@ -425,8 +427,10 @@ static Mesh *arrayModifier_doArray(ArrayModifierData *amd,
   }
   Object *end_cap_ob = amd->end_cap;
   if (end_cap_ob && end_cap_ob != ctx->object) {
+    if (start_cap_ob->type == OB_MESH && ctx->object->type == OB_MESH) {
       vgroup_end_cap_remap = BKE_object_defgroup_index_map_create(
           end_cap_ob, ctx->object, &vgroup_end_cap_remap_len);
+    }
 
     end_cap_mesh = BKE_modifier_get_evaluated_mesh_from_evaluated_object(end_cap_ob, false);
     if (end_cap_mesh) {