Fix #75 (ensure to return None if no filename)
Fix #75 (ensure to return None if no filename)

breunigs/SublimeFileBrowser,altairn5/SublimeFileBrowser,breunigs/SublimeFileBrowser,mrvkino/SublimeFileBrowser,mrvkino/SublimeFileBrowser,vprimachenko/SublimeFileBrowser,meganlkm/SublimeFileBrowser,aziz/SublimeFileBrowser,vprimachenko/SublimeFileBrowser,altairn5/SublimeFileBrowser