Exception thrown when comparing facts and unitRef is missing

[dgm9704]

System.NullReferenceException: Object reference not set to an instance of an object.
at Diwen.Xbrl.Fact.Equals(Fact other)
at System.Collections.Generic.GenericEqualityComparer1.Equals(T x, T y) at System.Collections.Generic.LinkedList1.Find(T value)
at Diwen.Xbrl.ListExtensions.ContentCompareReport[T](IList1 left, IList1 right)
at Diwen.Xbrl.InstanceComparer.FactComparison(Instance a, Instance b)
at Diwen.Xbrl.InstanceComparer.Report(Instance a, Instance b, ComparisonTypes comparisonTypes)
at XbrlCompare.Program.CompareAndReport(String inputReport, String outputReport, String comparisonReport, ComparisonTypes comparisonTypes)
at XbrlCompare.Program.Main(String[] args)

[dgm9704]

duplicate of #49