Google quietly announced on Google+ that starting September 12, 2016 the Google AdWords report may start showing null values in the quality score columns when the keywords are new or have insufficient impression or click data.
Google wrote, "null Quality Scores will appear for new keywords, as well as keywords that lack recent click and impression data."
Google added that "Null Quality Scores will be excluded if you use reports or automated rules that include a filter on the Quality Score column." If you want to show null scores you will need to check the new "Include keywords with quality scores of '--' " option when you set up your rule or filter.
Here is a screen shot:
Google said they recommend reviewing your reports, filters, rules and scripts that rely on Quality Scores before September 12th, 2016.
Forum discussion at Google+.