Hard to select directory for state file inputs

When you load a state file, one of the handy options is to select a directory from which to load files so that you can transfer a state file from one computer to another with a different file system. However, when you try to select a directory to use with the file browser, it is more difficult than it should be. You should be able to browse to the directory and hit OK, but you cannot.

To demonstrate, download this state file that loads a file in the Examples directory distributed with ParaView: FieldAtTime0.pvsm.

1. File -> Load State...
2. Select the FieldAtTime0.pvsm that you downloaded.
3. Change Load State Data File Options to Search files under a specified directory.
4. Click the ... button next to the new Data Directory option to open the file browser.
5. In the file browser, double-click the Examples directory in the list of common system directories. This is the directory you want to select.

At this point you should be able to just select OK to select this directory. But you can't. You have to go up a directory, then select the subdirectory, and then click OK, which is awkward as heck. Compare that to a normal system file browser in directory mode. (For example, you can see it in the CMake GUI when selecting a directory.)

The way it should work is for the OK button to be active if no files/directories are selected. In this case, the currently navigated folder will be selected.