Fix the unit test that attempts to construct a NumberWithUnits with no number.

Author: drgrice1

lib/Parser/Legacy/NumberWithUnits.pm

@@ -363,7 +363,7 @@ sub makeValue {
 	my $value   = shift;
 	my %options = (context => $self->context, @_);
 	my $num     = Value::makeValue($value, %options);
-	return bless $num, 'Parser::Legacy::FormulaWithUnits' if $num->classMatch('Formula');
+	return bless $num, 'Parser::Legacy::FormulaWithUnits' if defined $num && $num->classMatch('Formula');
 	Value::Error("A number with units must be a constant, not %s", lc(Value::showClass($num)))
 		unless Value::isReal($num);
 	bless $num, $options{class};

t/units/basic_parser.t

@@ -98,7 +98,7 @@ subtest 'Test error handling' => sub {
 	like(dies { NumberWithUnits(1) }, qr/You must provide units for your number/, 'No unit given');
 	like(
 		dies { NumberWithUnits('J') },
-		qr/You must provide units for your number/,
+		qr/A number with units must be a constant, not ''/,
 		'No value given, wants 2 arguments'
 	);
 };