test for empty flows, refs #1157

git-svn-id: http://svn.code.sf.net/p/sumo/code/trunk/sumo@15700 29f149b2-0c63-11e1-8f5c-a347f6a9acd0
fixing test for empty flows, refs #1157, #21

git-svn-id: http://svn.code.sf.net/p/sumo/code/trunk/sumo@15701 29f149b2-0c63-11e1-8f5c-a347f6a9acd0
Merge branch 'master' into planet