force-builds crashes with a traceback if you don't specify a test case name

[Glyph Lefkowitz]

This is pretty bad as it breaks the suggested bug workflow.

glyph@jaina:~/Projects/Twisted/trac-integration/tools★ python2.7 force-builds.py trial-stable-argument-order-5520-2 ''
 ↩ Thu Dec 6 23:33:43 PST 2012
2012-12-06 23:33:44-0800 [-] Log opened.
2012-12-06 23:33:44-0800 [-] Forcing...
2012-12-06 23:33:44-0800 [-] Traceback (most recent call last):
2012-12-06 23:33:44-0800 [-] File "force-builds.py", line 68, in <module>
2012-12-06 23:33:44-0800 [-] main()
2012-12-06 23:33:44-0800 [-] File "force-builds.py", line 58, in main
2012-12-06 23:33:44-0800 [-] url = url + '?' + '&'.join([k + '=' + urllib.quote(v) for (k, v) in args])
2012-12-06 23:33:44-0800 [-] File "/System/Library/Frameworks/Python.framework/Versions/2.7/lib/python2.7/urllib.py", line 1237, in quote
2012-12-06 23:33:44-0800 [-] raise TypeError('None object cannot be quoted')
2012-12-06 23:33:44-0800 [-] TypeError: None object cannot be quoted
 ↪ Thu Dec 6 23:33:44 PST 2012 (★ python2.7 force-builds.py trial-stable-argument-order-5520-2 '') (1 seconds elapsed)
[Error: 1]

[Tom Prince (tom.prince)]

Fixed: https://bazaar.launchpad.net/~twisted-dev/twisted-trac-integration/trunk/revision/72