Error doing Data Compare: "Unknown type found during storing data. Type: System.Data.SqlTypes.SqlDecimal" (4322822)

User created a Data Compare between two result sets. Each result set has one column decimal and one column float. 
If exists a null value on the float column, it throw an exception.

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Exception Information
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Error; Unknown type found during storing data. Type: System.Data.SqlTypes.SqlDecimal
Error; StackTrace : at Quest.DataCompare.PL.ComparisonKeeper.WriteValue(Object value, BinaryWriter writer, Boolean forSort)
at Quest.DataCompare.PL.ComparisonKeeper.AddRow(ComparisonStatus status, Int32& rowCount, Object[] valuesA, Object[] valuesB, Boolean[] cellEquality, Boolean duplicated)
at Quest.DataCompare.PL.ComparisonEngine.CompareRowData(Object[] rowSource, Object[] rowTarget, ComparisionOptions cmpOptions, SaveFlags saveFlags)
at Quest.DataCompare.PL.ComparisonEngine.CompareData(SaveFlags saveFlags, ComparisionOptions cmpOptions, String dataStoragePath, Guid sessionId, ICommandProgress overallProgress, ICommandProgress detailProgress, ConfirmRetryHandler retryHandler, Func`3 setValueLength, Boolean extractDataOnly, Int32 rowLimit)