Fix double confirmation dialog on overwriting a file
QFileDialog::getSaveFileUrl() by default asks for confirmation when selecting an existing file. It does this though on the very selected URL, while that URL might be modifed afterwards to enforce a ".kjc" extension. And duplicates the custom code to confirm overwriting the actual URL.
Seems there is no flag with QFileDialog to also have the extension enforced? So the custom code needs to stay, instead of having QFileDialog (platform implementations) handle that for us?