command: only avoid redrawing when old and new osd are both hidden

The `osd-overlay` command didn't trigger a redraw when the overlay was
set to hidden.
This is fine when the overlay was already hidden before that, but
transitioning from not hidden to hidden requires a redraw.

sub/osd_libass.c

@@ -572,6 +572,11 @@ void osd_set_external(struct osd_state *osd, struct osd_external_ass *ov)
         goto done;
     }
 
+    if (!entry->ov.hidden || !ov->hidden) {
+        obj->changed = true;
+        osd->want_redraw_notification = true;
+    }
+
     entry->ov.format = ov->format;
     if (!entry->ov.data)
         entry->ov.data = talloc_strdup(entry, "");
@@ -585,11 +590,6 @@ void osd_set_external(struct osd_state *osd, struct osd_external_ass *ov)
 
     update_external(osd, obj, entry);
 
-    if (!entry->ov.hidden) {
-        obj->changed = true;
-        osd->want_redraw_notification = true;
-    }
-
     if (zorder_changed) {
         qsort(obj->externals, obj->num_externals, sizeof(obj->externals[0]),
               cmp_zorder);