Unbreak tests

Looks like sqlobject support for notNull is broken: with 0.12.4 the
description field of a newly created task is None, not "", which
caused TextListRenderer to assume the task had a description.

src/yokadi/textlistrenderer.py

@@ -71,7 +71,7 @@ def __init__(self, width, cryptoMgr):
 
     def __call__(self, task):
         keywords = task.getUserKeywordsNameAsString()
-        hasDescription = task.description != ""
+        hasDescription = task.description is not None and task.description != ""
         title = self.cryptoMgr.decrypt(task.title)
         # Compute title, titleWidth and colorWidth
         maxWidth = self.width