message: make videostreamingstate optional
diff: <param name="systemContext" type="SystemContext" mandatory="true">
  <description>See SystemContext</description>
  </param>
  - <param name="videoStreamingState" type="VideoStreamingState" mandatory="true">
  + <param name="videoStreamingState" type="VideoStreamingState" mandatory="false" defvalue="STREAMABLE">
  <description>See VideoStreamingState. If it is NOT_STREAMABLE, the app must stop streaming video to SDL.</description>
  </param>
  </function>
  