SimpleChooserControl does not handle some non-existant paths

[VirtualTim]

SimpleChooserControl contains the following:

PreferencesFX/preferencesfx/src/main/java/com/dlsc/preferencesfx/formsfx/view/controls/SimpleChooserControl.java

Lines 131 to 135 in 4c65404

	if (!new File(previousPath).isDirectory()) {
	Path path = Paths.get(previousPath);
	previousPath = path.getParent().toAbsolutePath().toString();
	}
	currentInitialDirectory = new File(previousPath);

There's two problems here:

1. If the parent also doesn't exist (ie: C:\a\b) a NPE is thrown and nothing is displayed
2. If that path is not valid, and does not contain a parent (ie: a), a NPE is thrown and nothing is displayed

I think this could be fixed by changing:

if (!new File(previousPath).isDirectory()) {
  Path path = Paths.get(previousPath);
  previousPath = path.getParent().toAbsolutePath().toString();

to

while (!new File(previousPath).isDirectory()) {
  Path path = Paths.get(previousPath);
  Path potentialParent = path.getParent();
  previousPath = potentialParent != null ? potentialParent.toAbsolutePath().toString() : null;