[#516] Check for lastSurveyalInstanceId not null

* in old data, this field can be null. In that case
the data will be considered private and included
in the private clusters.
[#518] Release notes 1.6.14.3
Merge pull request #517 from akvo/1.6.14/hotfix

[#516] Check for lastSurveyalInstanceId not null
Merge branch 'release/1.6.14'