Handling of 3D coordinates with Null Z-values to avoid jsonld renderi…

[jwallace94]

…ng errors

Overview

There is an issue with jsonld crashing on data which is a 3D point with a z-coordinate value of "Null". The value -99999 has been cited as an established value of "unknown" by MEGIS and this will fix the excessive logs generated and the error on the frontend.

Related Issue / discussion

https://gajira.atlassian.net/browse/DATA-1452

Additional information

Dependency policy (RFC2)

• I have ensured that this PR meets RFC2 requirements

Updates to public demo

• I have ensured that breaking changes to the pygeoapi master demo server have been addressed
  • https://github.com/geopython/demo.pygeoapi.io/blob/master/services/pygeoapi_master/local.config.yml

Contributions and licensing

(as per https://github.com/geopython/pygeoapi/blob/master/CONTRIBUTING.md#contributions-and-licensing)

• I'd like to contribute [feature X|bugfix Y|docs|something else] to pygeoapi. I confirm that my contributions to pygeoapi will be compatible with the pygeoapi license guidelines at the time of contribution
• I have already previously agreed to the pygeoapi Contributions and Licensing Guidelines