chore(pwa) Check if manifest exists

index.html

@@ -22,10 +22,32 @@
                 : pathname.substring(0, contextRootEndIndex + 1)
             );
         }
+
+
+        function getPwaLink() {
+            return window.location.origin + contextRoot(window.location.pathname) + 'manifest.json'
+        }
+
+        function validateLink(link) {
+            return fetch(link)
+                .then(resp => resp.ok && resp.headers?.get('Content-type')=== 'application/json')
+                .catch(e => false);
+        }
+
         window.EXCALIDRAW_ASSET_PATH = 'libs/';
-        // Dynamically generate the manifest location URL. It must be served from the document origin, and we may have
-        // the base pointing to the CDN. This way we can generate a full URL which will bypass the base.
-        document.querySelector('#manifest-placeholder').setAttribute('href', window.location.origin + contextRoot(window.location.pathname) + 'manifest.json');
+
+        const pwaManifestLink = getPwaLink();
+        validateLink(pwaManifestLink).then(success => {
+            const manifestElement = document.querySelector('#manifest-placeholder');
+            if (success) {
+                // Dynamically generate the manifest location URL. It must be served from the document origin, and we may have
+                // the base pointing to the CDN. This way we can generate a full URL which will bypass the base.
+                manifestElement.setAttribute('href', pwaManifestLink)
+            } else {
+                manifestElement.remove();
+            }
+        });
+
 
         document.addEventListener('DOMContentLoaded', () => {
             if (!JitsiMeetJS.app) {