turn NPE into a throw

src/matrix-to.js

@@ -239,9 +239,13 @@ export function makeUserPermalink(userId) {
 export function makeRoomPermalink(roomId) {
     const permalinkBase = `${baseUrl}/#/${roomId}`;
 
+    if (!roomId) {
+        throw new Error("can't permalink a falsey roomId");
+    }
+
     // If the roomId isn't actually a room ID, don't try to list the servers.
     // Aliases are already routable, and don't need extra information.
-    if (!roomId || roomId[0] !== '!') return permalinkBase;
+    if (roomId[0] !== '!') return permalinkBase;
 
     const client = MatrixClientPeg.get();
     const room = client.getRoom(roomId);