add test for QFileDialog::getExistingDirectory / bug?

[Gregor Mi]

Hi,

with 2c1ee08a21a1f16f9c2523718224598de8fc0d4f I added a test for
QFileDialog::getExistingDirectory.

When I execute

./qfiledialogtest --staticFunction getExistingDirectory

then a dialog opens that lets the user select files but not directories.
This seems to be a bug.

Greetings

Gregor