vchoi_fork

[svn-r9297] Purpose:
Bug fix.

Description:
Code would attempt to Calloc with zero count when a simple expression
that has no x term.  That resulted in NULL for some platform (like AIX).
That appeared as a failure treated as out of space.

Solution:
Checked if count is larger than 0 before making the calloc request.

Platforms tested:
Tested in copper (pp) where the failure appeared.  Also in eirene
as double check.  No h5committest as the change is trivial.