Fixes issue #70 - Invite others reports null when pressed too early.

app.js

@@ -1213,7 +1213,6 @@ function buttonClick(id, classname) {
  * @param messageString the text of the message
  */
 function openMessageDialog(titleString, messageString) {
-    console.log("OPEN MESSAGE DIALOG");
     $.prompt(messageString,
         {
             title: titleString,
@@ -1288,6 +1287,11 @@ function openLockDialog() {
  * Opens the invite link dialog.
  */
 function openLinkDialog() {
+    if (roomUrl == null)
+        openMessageDialog(  "Invite others",
+                            "Your conference is currently being created."
+                            + " Please try again in a few seconds.");
+    else
         $.prompt('<input id="inviteLinkRef" type="text" value="' +
                 encodeURI(roomUrl) + '" onclick="this.select();" readonly>',
                 {