Math::BigFloat fixes

[Chris Travers <..hidden..>]

Hi all;

Thanks to the generous assistance from David Bandel, I have been
successful at reproducing the issue with the recent
Math::BigFloat-induced bugs.  I have further been able to correct it
at least in my own instance.

Description of issue:

1.2:  When you try to update an existing transaction or print a sales
invoice you get an error similar to:

menu.pl:92: Can't call method "is_zero" on an undefined value at
/usr/local/lib/perl5/site_perl/5.12.4/Math/BigInt.pm line 1197

In 1.3:  You get an internal server error after selecting a customer
or vendor for an AR/AP transaction.  The logs reference a similar
error to the above message.

If you are not yet experiencing this error, please avoid updating Perl
dependencies while the fix is fully vetted by those who are currently
facing this issue.  We expect the next versions of both 1.2 and 1.3 to
have this error corrected.

If you are experiencing this error, please update to the latest files
from SVN on your branch.  (branches/1.2 and branches/1.3).  If you are
unable to apply the fix from SVN, please  contact me and we'll see
what we need to do about getting you a snapshot.  Please note that
such an update puts you in between releases, meaning that you are
getting relatively untested bugfixes.  Please put this through some
testing on a test server before putting it into production.

Best Wishes,
Chris Travers