Fix(unreported): LineArt curve objects garbled result.

This is caused by line art loading curve objects twice from curve and converted mesh instances (when instance option is on). Now only load mesh when instance option is on.

source/blender/gpencil_modifiers/intern/lineart/lineart_cpu.c

@@ -2168,6 +2168,12 @@ static void lineart_main_load_geometries(
       use_mesh = use_ob->data;
     }
     else {
+      /* If DEG_ITER_OBJECT_FLAG_DUPLI is set, the curve objects are going to have a mesh
+       * equivalent already in the object list, so ignore converting the original curve in this
+       * case. */
+      if (allow_duplicates) {
+        continue;
+      }
       use_mesh = BKE_mesh_new_from_object(depsgraph, use_ob, true, true);
     }