1.1 - Fix FileWriterBase:getScanNumber() exception to provide enough info. BLX-35

In completing BLX-35 it wasn't clear why getScanNumber was throwing an
exception as the same exception was thrown whether scanInformation was
null or scanInformation.getScanNumber() was null.
Merge remote-tracking branch 'i10gda_8.26a/1.1-I10' into 1.1-I10