Fixed SVG export and added regression test

MANIFEST

@@ -81,6 +81,7 @@ t/shells.t
 t/slice.t
 t/skirt_brim.t
 t/support.t
+t/svg.t
 t/vibrationlimit.t
 utils/amf-to-stl.pl
 utils/file_info.pl

lib/Slic3r/Print.pm

@@ -488,13 +488,15 @@ sub export_svg {
     $self->init_extruders;
     
     $_->slice for @{$self->objects};
-    $self->arrange_objects;
     
+    my $fh = $params{output_fh};
+    if ($params{output_file}) {
         my $output_file = $self->expanded_output_filepath($params{output_file});
         $output_file =~ s/\.gcode$/.svg/i;
+        Slic3r::open(\$fh, ">", $output_file) or die "Failed to open $output_file for writing\n";
+        print "Exporting to $output_file..." unless $params{quiet};
+    }
     
-    Slic3r::open(\my $fh, ">", $output_file) or die "Failed to open $output_file for writing\n";
-    print "Exporting to $output_file...";
     my $print_size = $self->size;
     print $fh sprintf <<"EOF", unscale($print_size->[X]), unscale($print_size->[Y]);
 <?xml version="1.0" encoding="UTF-8" standalone="yes"?>
@@ -563,7 +565,7 @@ EOF
     
     print $fh "</svg>\n";
     close $fh;
-    print "Done.\n";
+    print "Done.\n" unless $params{quiet};
 }
 
 sub make_skirt {

t/svg.t

@@ -0,0 +1,23 @@
+use Test::More tests => 1;
+use strict;
+use warnings;
+
+BEGIN {
+    use FindBin;
+    use lib "$FindBin::Bin/../lib";
+}
+
+use Slic3r;
+use Slic3r::Test;
+
+{
+    my $print = Slic3r::Test::init_print('20mm_cube');
+    eval {
+        my $fh = IO::Scalar->new(\my $gcode);
+        $print->export_svg(output_fh => $fh, quiet => 1);
+        $fh->close;
+    };
+    ok !$@, 'successful SVG export';
+}
+
+__END__