Update parser.py

issue #348

src/icalendar/parser.py

@@ -334,6 +334,8 @@ class Contentline(str):
             if not name:
                 raise ValueError('Key name is required')
             validate_token(name)
+            if not value_split:
+                value_split = i
             if not name_split or name_split + 1 == value_split:
                 raise ValueError('Invalid content line')
             params = Parameters.from_ical(st[name_split + 1: value_split],