De-scope unsaved draft top-level comments from patch number

Bug: Issue 6373
Change-Id: I4d6b9cf773513fe24dc166c89848e93d39375466
diff --git a/polygerrit-ui/app/elements/change/gr-reply-dialog/gr-reply-dialog.js b/polygerrit-ui/app/elements/change/gr-reply-dialog/gr-reply-dialog.js
index 8218b43..7d7c3e2 100644
--- a/polygerrit-ui/app/elements/change/gr-reply-dialog/gr-reply-dialog.js
+++ b/polygerrit-ui/app/elements/change/gr-reply-dialog/gr-reply-dialog.js
@@ -604,7 +604,7 @@
       if (!this.change) { return {}; }
       return {
         changeNum: this.change._number,
-        patchNum: this.patchNum,
+        patchNum: '@change',
         path: '@change',
       };
     },
diff --git a/polygerrit-ui/app/elements/change/gr-reply-dialog/gr-reply-dialog_test.html b/polygerrit-ui/app/elements/change/gr-reply-dialog/gr-reply-dialog_test.html
index d4f7489..9f5512b 100644
--- a/polygerrit-ui/app/elements/change/gr-reply-dialog/gr-reply-dialog_test.html
+++ b/polygerrit-ui/app/elements/change/gr-reply-dialog/gr-reply-dialog_test.html
@@ -354,7 +354,7 @@
     test('_getStorageLocation', () => {
       const actual = element._getStorageLocation();
       assert.equal(actual.changeNum, changeNum);
-      assert.equal(actual.patchNum, patchNum);
+      assert.equal(actual.patchNum, '@change');
       assert.equal(actual.path, '@change');
     });