fluent 0.9.1

• Forbid messages with null values and no attributes. (#299)

  Fix a parser behavior which caused it to parse messages without values nor attributes as "message-id": null. This skewed the return values of FluentBundle.hasMessage which would report true for messages which were null. This, in turn, would break code which assumed FluentBundle.getMessage would always return non-null values if it was guarded by a call to hasMessage first.