Fix issue where listener wasn't removed and logic was called many times

(reference #53 )

Super.Human.Portal_Royale/src/resources/nomadhelper.html

@@ -17,11 +17,11 @@
         const hrefUrl = new URL(link);
 
         if (navigator && navigator.serviceWorker && navigator.serviceWorker.controller) {
-       		navigator.serviceWorker.onmessage = function(event) {
+        		var messageFunction = function(event) {
     				if (event.data.type == 'numberOfWindowClients') {
     					if (event.data.clientCount > 1)
     					{   		
-							navigator.serviceWorker.controller.postMessage({
+						navigator.serviceWorker.controller.postMessage({
 							type: 'openNotesUri',
 							payload: {
 								notesUri: decodeURIComponent(
@@ -31,17 +31,20 @@
 								)
 							}
 						});
-						           
+
            			    window.top.postMessage('[Success] Successfully called openNotesUri', '*');
 					}
 					else
 					{
+						console.error('Nomad Window is closed');
 						window.top.postMessage('[Error] Nomad Window is closed', '*');
 					}
-
+
+       			    navigator.serviceWorker.removeEventListener('message', messageFunction);
     				}
         		};
-
+
+       		navigator.serviceWorker.addEventListener('message', messageFunction);
 			navigator.serviceWorker.controller.postMessage({type: 'numberOfWindowClients'});
         } else {
             console.error('No service worker registered');