Bug in eval of url() when spaces are present around the '' quoted string

[nvkelso]

This works:
polygon-pattern-file: url('icons/halftone2.png');

But this doesn't:
polygon-pattern-file: url( 'icons/halftone2.png' );

Error:

Exception: Image file needs to be a working, fetchable resource, not file:///home/nate/public_html/toner/mapnik/ 'icons/halftone2.png'