Refactored Print::validate() method to not throw an exception, but

to return a string with an error message instead. This was necessary
to avoid a hang-up on some Strawberry Perl distributions, when
a perl "croak" function is called after a C++ exception is caught.

lib/Slic3r/Print.pm

@@ -450,4 +450,13 @@ sub expanded_output_filepath {
     return $self->placeholder_parser->process($path);
 }
 
+# Wrapper around the C++ Slic3r::Print::validate()
+# to produce a Perl exception without a hang-up on some Strawberry perls.
+sub validate
+{
+    my $self = shift;
+    my $err = $self->_validate;
+    die $err . "\n" if (defined($err) && $err ne '');
+}
+
 1;