Fix T100578: Surface Deform modifier displays wrong in editmode

This was the case when the "Show in Editmode" option was used and a
vertexgroup affected the areas.

Probably an oversight in {rBdeaff945d0b9}?, seems like deforming
modifiers always need to call `BKE_mesh_wrapper_ensure_mdata` in
`deformVertsEM` when a vertex group is used.

Maniphest Tasks: T100578

Differential Revision: https://developer.blender.org/D15756

source/blender/modifiers/intern/MOD_surfacedeform.c

@@ -1603,6 +1603,11 @@ static void deformVertsEM(ModifierData *md,
     mesh_src = MOD_deform_mesh_eval_get(ctx->object, em, mesh, NULL, verts_num, false, false);
   }
 
+  /* TODO(@campbellbarton): use edit-mode data only (remove this line). */
+  if (mesh_src != NULL) {
+    BKE_mesh_wrapper_ensure_mdata(mesh_src);
+  }
+
   surfacedeformModifier_do(md, ctx, vertexCos, verts_num, ctx->object, mesh_src);
 
   if (!ELEM(mesh_src, NULL, mesh)) {