components/app: make showNotification return null on error

We'll do more involved stuff with notifications soon, and don't
want to deal with buggy notification objects.

components/app.js

@@ -120,7 +120,7 @@ function fillConnectParams(params) {
 
 function showNotification(title, options) {
 	if (!window.Notification || Notification.permission !== "granted") {
-		return new EventTarget();
+		return null;
 	}
 
 	// This can still fail due to:
@@ -129,7 +129,7 @@ function showNotification(title, options) {
 		return new Notification(title, options);
 	} catch (err) {
 		console.error("Failed to show notification: ", err);
-		return new EventTarget();
+		return null;
 	}
 }
 
@@ -524,12 +524,14 @@ export default class App extends Component {
 					requireInteraction: true,
 					tag: "msg,server=" + serverID + ",from=" + msg.prefix.name + ",to=" + bufName,
 				});
+				if (notif) {
 					notif.addEventListener("click", () => {
 						// TODO: scroll to message
 						this.switchBuffer({ server: serverID, name: bufName });
 					});
 				}
 			}
+		}
 		if (msg.command === "INVITE" && client.isMyNick(msg.params[0])) {
 			msgUnread = Unread.HIGHLIGHT;
 
@@ -543,6 +545,7 @@ export default class App extends Component {
 					title: "Accept",
 				}],
 			});
+			if (notif) {
 				notif.addEventListener("click", (event) => {
 					if (event.action === "accept") {
 						let stored = {
@@ -560,6 +563,7 @@ export default class App extends Component {
 					}
 				});
 			}
+		}
 
 		// Open a new buffer if the message doesn't come from me or is a
 		// self-message