[FIX] Workflow function activities explode if they contain empty lines.

bzr revid: tpa@tinyerp.com-20120905102821-8q6d42d5p0xudxmv

openerp/workflow/wkf_expr.py

@@ -44,7 +44,7 @@ class Env(dict):
 def _eval_expr(cr, ident, workitem, action):
     ret=False
     assert action, 'You used a NULL action in a workflow, use dummy node instead.'
-    for line in action.split('\n'):
+    for line in filter(lambda action: action != "", action.split('\n')):
         line = line.strip()
         uid=ident[0]
         model=ident[1]