QFileOpenDialog native dialog's [Open} button is enabled when there are no files selected

Creating a new QFileDialog, with:

• a file mode of QtFileDialog::ExistingFiles.
• a name filter set via setNameFilter()

When exec() is run on the dialog, the native Qt file dialog appears (as expected). Navigate to a directory, and select one file. The [Open] button is enabled, as expected. If you delete the file from the File name edit box, the [Open] button becomes disabled, again as expected. However, if you select more than one file (via <ctrl> + click on various files displayed in the list), then delete all of them from the File name edit box, the Open button is not re-rendered in its disabled rendering; it appears to be enabled. Clicking on it performs no activity, although the button is rendered as pressend when the mouse is clicked on it (or if the <space> bar is pressed when the [Open] button has focus).