fdo#74014: Another attempt to reproduce this bug in test.

But still not reproducible in test. Only in the UI. This is maddening.
I give up for now.

Change-Id: I88e6f4ed19856cf81abdf188dc22a5012e8c4a28
Ensure that vector array has a numeric array of NaN's for empty range.

With this change, we ensure that mpNumArray is never NULL even when the
range consists entirely of empty cells.  For an empty range, mpNumArray
will be non-NULL and filled with NaN's while mpStrArray will be NULL.

Change-Id: If5cead26ebe917af150cf7e39e17afe3f310beb7