Fix error when path is no valid directory

[Siedlerchr]

Fixes the exception Folder parameter must be a valid folder
Internal fix, 4.0.0 only
When no working directory is set and last used path was an actual file, File Dialog could not be opened.
Fixes #2522

[stefan-kolb]

LGTM, but what is the normal behavior for system dialogs? If I select a file ijnstead of a directory, is it possible and selects the parent folder or is the select button inactive?

[Siedlerchr]

@stefan-kolb My fix has only impact when opening the dialog, that it opens in a directory without an exception . It has no impact on the selection of files etc.

Parent does not mean parent directory, but the directory itself (the parent of the file):
Example: Your last selected file was X:\abc\defg.pdf
When you try to set the initalDirectory to this complete path (including filename), it gives an exception, because it is obviously no a folder (directory). Therefore, the fix now sets the dir to X:\abc (which is the parent of X:\abc\defg.pdf

[stefan-kolb]

Ah **** sorry for that! Yeah I know, i was aware of that.