fixed data null on batch send error

[GerritK]

No description provided.

[joostvunderink]

Hi Gerrit,

thanks for your pull request. Could you explain in a few sentences which problem this change solves, so I can write proper release notes?

Thanks.

[GerritK]

Hi Joost,

the 'data' value could be null if there was an error in network transport. As http state there is -1 and the promise does not complete.

Greets.