Trigger error message by throwing OperationFailedException to explain

that joining chat room failed.

src/net/java/sip/communicator/impl/protocol/irc/OperationSetMultiUserChatIrcImpl.java

@@ -169,9 +169,21 @@ public ChatRoom createChatRoom(
             final Map<String, Object> roomProperties)
         throws OperationFailedException,
                OperationNotSupportedException
+    {
+        try
         {
             return findOrCreateRoom(roomName);
         }
+        catch (IllegalArgumentException e)
+        {
+            String message =
+                IrcActivator.getResources().getI18NString(
+                    "service.gui.CREATE_CHAT_ROOM_ERROR", new String[]
+                    { roomName });
+            throw new OperationFailedException(message,
+                OperationFailedException.ILLEGAL_ARGUMENT, e);
+        }
+    }
 
     /**
      * Returns a reference to a chatRoom named <tt>roomName</tt>.