Donors where IsDonorPhenotypeUnrepresented is true do not have value for MatchProbabilitiesPerLocus.OverallMatchCount

[mmelchers]

Describe the bug
As a search coordinator I expect that even "inexplicable" donors (where IsDonorPhenotypeUnrepresented= true) have a match class assigned. This is currently not the case for ATLAS

To Reproduce
Steps to reproduce the behaviour:

1. Start a search with many search results
2. Find a donor where IsDonorPhenotypeUnrepresented= true
3. check value for MatchProbabilitiesPerLocus.OverallMatchCount

Expected behaviour
MatchProbabilitiesPerLocus.OverallMatchCount has a numerical value

Actual behaviour
MatchProbabilitiesPerLocus.OverallMatchCount = null

Additional context
Since we are using the match probabilities from ATLAS, we were told to also use the match probability based overallMatchCount

[zabeen]

Discussed this with @mmelchers

Atlas cannot determine a predicted match count value where it was unable to calculate match probabilities due to either patient or donor being unrepresented by the HLA HF set.

The consumer service can instead fall back on the potential match count, which is based on P groups.