Fixed public upload error that prevents upload

Public upload is broken because the file_upload_param variable expected
to exist by public.js didn't.

This fix sets the variable scope to the window to make it accessible
outside.

apps/files/js/file-upload.js

@@ -348,4 +348,5 @@ $(document).ready(function() {
 			$('#new>a').click();
 		});
 	});
+	window.file_upload_param = file_upload_param;
 });