Fix utterly broken versionning code for weight modifier.

Own fault in some recent patch rewiew/commit...

source/blender/blenloader/intern/versioning_290.c

@@ -249,7 +249,7 @@ void blo_do_versions_290(FileData *fd, Library *UNUSED(lib), Main *bmain)
     LISTBASE_FOREACH (Object *, ob, &bmain->objects) {
       LISTBASE_FOREACH (ModifierData *, md, &ob->modifiers) {
         if (md->type == eModifierType_WeightVGEdit) {
-          md->flag &= ~MOD_WVG_EDIT_WEIGHTS_NORMALIZE;
+          ((WeightVGEditModifierData *)md)->edit_flags &= ~MOD_WVG_EDIT_WEIGHTS_NORMALIZE;
         }
       }
     }