Close delete dialog after confirming deleting change

Currently when user confirms delete dialog, user ends up in dashboard
with gray layer. This is artefact of not closing delete dialog.

Bug: Google b/194328301

Change-Id: I638cf988c65e5f484408f8be101df2f621b36a99
diff --git a/polygerrit-ui/app/elements/change/gr-change-actions/gr-change-actions.ts b/polygerrit-ui/app/elements/change/gr-change-actions/gr-change-actions.ts
index a0b1794..fce7db9 100644
--- a/polygerrit-ui/app/elements/change/gr-change-actions/gr-change-actions.ts
+++ b/polygerrit-ui/app/elements/change/gr-change-actions/gr-change-actions.ts
@@ -1486,6 +1486,7 @@
   }
 
   _handleDeleteConfirm() {
+    this._hideAllDialogs();
     this._fireAction(
       '/',
       assertUIActionInfo(this.actions[ChangeActions.DELETE]),