Fixes related to service worker (#191)

1. Fix CSS causing setting button to be offscreen on Safari
2. Fix "this page has been updated" message on 2nd page loads

Author: ShukantPal

core/webdoc-default-template/src/protocol/index.js

@@ -69,7 +69,8 @@ export class webdocService {
         });
       }
 
-      this.stale = true;
+      // The manifest changed from a previous non-null value
+      if (manifest) this.stale = true;
     }
 
     this.offline = offline;

core/webdoc-default-template/src/styles/header.scss

@@ -13,7 +13,7 @@
     display: grid;
     grid-template-rows: 100%;
     grid-template-columns: fit-content(100%) minmax(0, max-content) fit-content(100%) minmax(0, 1fr);
-    height: 100vh;
+    height: 100%;
     overflow: hidden;/* child element must overflow/scroll on their own */
 
     @media only screen and (max-width: 800px) {