[longomatch] Fix non editable behaviour when a chooser is cleared.

[Andoni Morales Alastruey <amorales src gnome org>]

commit f9f8a94188004f7fb3224c2ea94675a8bc23abb8
Author: Julien Moutte <julien fluendo com>
Date:   Wed Mar 18 18:49:29 2015 +0100

    Fix non editable behaviour when a chooser is cleared.
    
    Indeed if a valid file was chosen in the file chooser and then cleared, we should put an invalid file 
path in the media file otherwise CheckFiles would return true even though the file chooser entry is supposed 
to be empty.

 .../Gui/Component/MediaFileSetSelection.cs         |    3 +++
 1 files changed, 3 insertions(+), 0 deletions(-)
---
diff --git a/LongoMatch.GUI/Gui/Component/MediaFileSetSelection.cs 
b/LongoMatch.GUI/Gui/Component/MediaFileSetSelection.cs
index d34a54f..cb5c359 100644
--- a/LongoMatch.GUI/Gui/Component/MediaFileSetSelection.cs
+++ b/LongoMatch.GUI/Gui/Component/MediaFileSetSelection.cs
@@ -118,6 +118,9 @@ namespace LongoMatch.Gui.Component
                                MediaFile mf = fileChoosers [i].MediaFile;
                                if (mf != null) {
                                        fileSet.Replace (fileSet [i], mf);      
+                               } else {
+                                       // Make sure that CheckFiles will not return true for this 
MediaFile...
+                                       fileSet [i].FilePath = null;
                                }
                        }
                }