Issue with non-numeric data in chart value axes

[jmcnamara]

Reported by @msmcgillis.

Non-numeric data in chart value axes should be treated as zero or else Excel will generate warnings when reading the data. Example:

use Excel::Writer::XLSX;

gen(["-nan",3,4,5,"inf"],"fail.xlsx"); # Excel will not show any chart at all
gen([0,3,4,5,0],"works.xlsx");         # this works but shouldn't be necessary


sub gen {
  my $ss=Excel::Writer::XLSX->new($_[1]);
  my $wsd=$ss->add_worksheet("Data");
  $wsd->write("A1",$_[0]); # places text in chart need to be 0
  my $wsc=$ss->add_worksheet("Chart");
  my $chart=$ss->add_chart(type=>"line",embedded=>1);
  $chart->add_series(values=>'=Data!$A$1:$E$1');
  $wsc->insert_chart("A2",$chart);
}

[msmcgillis]

I pulled your latest master and ran a number of test cases for data that was giving me problems. Looks like your new code always produced nice charts regardless of the string issue. Once I see a release go out with this in it I will probably do another merge of your released version with my branch to pick it up.

Thanks!

[jmcnamara]

Pushed to CPAN.