Fix exporting to PNG.

Upstream bug: https://code.google.com/p/evoluspencil/issues/detail?id=545
Gentoo bug #468888

--- usr/share/pencil/content/pencil/common/svgRasterizer.js
+++ usr/share/pencil/content/pencil/common/svgRasterizer.js
@@ -261,7 +261,7 @@
               createInstance(Components.interfaces.nsIWebBrowserPersist);
 
     persist.progressListener = persistListener;
-    persist.saveURI(uri, null, null, null, null, localFile);
+    persist.saveURI(uri, null, null, null, null, localFile, null);
     //persist.cancelSave();
 }