SingleScalarHydrator reports ambiguous error.

In the previous situation there is a combined test (A or B) which result in the same error message. However the error message does not fit with condition B (see code).

Looking at the function description the function should return a __a single scalar value__.

On a side note:
1. it's weird that this method call is used gatherScalarRowData() as it seems to fetch an entire row.
2. there is no function to fetch a single row.