Do not re-initialise toast displayed time when navigating

We maintain when last displayed toast was clicked to navigate users
to the next file if the click happens within 5s.
Fix the bug where last displayed time was being incorrectly assigned
a value when navigating to the next file.

Issue: Bug 13714
Change-Id: I5266e32558dab856f1d75ea3bb15decb23000a4e
diff --git a/polygerrit-ui/app/elements/diff/gr-diff-cursor/gr-diff-cursor.ts b/polygerrit-ui/app/elements/diff/gr-diff-cursor/gr-diff-cursor.ts
index 684a58a..43ed77f 100644
--- a/polygerrit-ui/app/elements/diff/gr-diff-cursor/gr-diff-cursor.ts
+++ b/polygerrit-ui/app/elements/diff/gr-diff-cursor/gr-diff-cursor.ts
@@ -226,9 +226,10 @@
             bubbles: true,
           })
         );
+      } else {
+        this.lastDisplayedNavigateToNextFileToast = Date.now();
+        fireAlert(this, 'Press n again to navigate to next unreviewed file');
       }
-      this.lastDisplayedNavigateToNextFileToast = Date.now();
-      fireAlert(this, 'Press n again to navigate to next unreviewed file');
     }
 
     this._fixSide();