Fixed a bug in the directory navigation gui. If you tried to go

into a drive on windows that wasn't mounted you got an error.
This is now fixed.

--HG--
extra : convert_revision : svn%3Afdd8eb12-d10e-0410-9acb-85c331704f74/trunk%402503

dlib/gui_widgets/widgets.h

@@ -1819,8 +1819,11 @@ namespace dlib
                     path = old_path;
                     cur_dir = old_cur_dir;
                 }
+                else
+                {
 
                 sob[cur_dir]->set_checked();
+                }
             }
 
             void on_dirs_click (