FileProperty returns a non-empty string even if nothing is typed in in the GUI

[mantid-builder]

Original Reporter: @jzikovsky

Steps to reproduce:

• Launch MantidPlot
• Execute LoadEventPreNexus
• Clear all the filenames.
• Click run.

Look in the Results log window: You will see this:

Algorithm: LoadEventPreNeXus v1
Parameters:
Name: EventFilename, Value: /home/janik/Code/Mantid/Code/Mantid/release/, Default?: No, Direction: Input
Name: PulseidFilename, Value: /home/janik/Code/Mantid/Code/Mantid/release/, Default?: No, Direction: Input
Name: MappingFilename, Value: /home/janik/Code/Mantid/Code/Mantid/release/, Default?: No, Direction: Input
Name: InstrumentFilename, Value: /home/janik/Code/Mantid/Code/Mantid/release/, Default?: No, Direction: Input

... so all the empty filenames were converted to the path where mantidplot lives (although I launched from /home/janik/Code/Mantid/Code/Mantid/debug/ ) so I don't know why it points there.

This later causes a maddening error in LoadEventPreNeXus if the mapping filename is not specified (it tries to load the folder or something)

Martyn, I assigned it to you since you last touched FileProperty, but I'm not sure if you are responsible for it; please reassign as needed.

[mantid-builder]

This issue was originally trac ticket 1458