Empty error message when reading UI file fails

When trying to open a broken UI file an empty error message box appears. Although it isn't quite clear if the message is really empty because as seen in the picture it only displays the error symbol and cannot be resized.

The console displays the following debug message when trying to parse the file:

Designer: An error has occurred while reading the UI file at line 102, column 8: Unexpected element item

(The broken UI file was caused by manual editing, so this is not an issue here).

Regards
Alex