do not fail creating subjects list on bad data

tabellio/contact/form.py

@@ -47,8 +47,13 @@ class View(grok.View):
 def get_possible_subjects(context):
     terms = []
     for line in context.context.subjects.splitlines():
-        topic, email = line.strip().split('|')
+        try:
+            topic, email = line.strip().split('|')
+        except ValueError:
+            continue
         terms.append(SimpleVocabulary.createTerm(topic, topic.encode('ascii', 'replace'), topic))
+    if len(terms) == 0:
+        terms.append(SimpleVocabulary.createTerm('-', '-', '-'))
     return SimpleVocabulary(terms)
 
 class IEffectiveContact(interface.Interface):