Modified get_pq_tests_run method to provide default if necessary.
Modified get_pq_tests_run method to provide default if necessary.

This method relys on using an up-to-date version of ga-neo-landsat-processor,
which cannot be garunteed yet. The fix checks for an attribute error, and
provides a default for PQA datasets if needed.

modified:   landsat_dataset.py

smr547/agdc,jeremyh/agdc,sixy6e/agdc,GeoscienceAustralia/agdc,ama-jharrison/agdc,alex-ip/agdc,alex-ip/agdc,sixy6e/agdc,jeremyh/agdc,smr547/agdc,GeoscienceAustralia/agdc,ama-jharrison/agdc