Bugfix in case commandline text is empty.

gui/Scyther/XMLReader.py

@@ -295,6 +295,7 @@ class XMLReader(object):
             elif event.tag == 'system':
                 attack.match = int(event.find('match').text)
                 for term in event.find('commandline'):
+                    if term.text != None:
                         if attack.commandline != '':
                             attack.commandline += ' ' 
                         attack.commandline += term.text