make a more informative error dialog in mucjoindlg #1

Author: kapad

src/mucjoindlg.cpp

@@ -331,7 +331,12 @@ void MUCJoinDlg::doJoin(MucJoinReason r)
     }
 
     if (!account_->groupChatJoin(host, room, nick, pass, !ui_.ck_history->isChecked())) {
-        QMessageBox::information(this, tr("Error"), tr("You are in or joining this room already!"));
+        QMessageBox::information(
+                this,
+                tr("Error"),
+                tr("You are in or joining this room already!\n\n- Account: %1\n-    Room: %2\n"
+                  ).arg( account_->jid().bare(), j.bare() )
+            );
         return;
     }