Don't leak the CRDocHandler.

==988== 104 (92 direct, 12 indirect) bytes in 1 blocks are definitely lost in loss record 4,805 of 5,382
==988==    at 0x402AD89: malloc (vg_replace_malloc.c:236)
==988==    by 0x4B40BDA: standard_malloc (gmem.c:85)
==988==    by 0x4053A15: rsvg_parse_cssbuffer (rsvg-styles.c:1128)
==988==    by 0x4056644: rsvg_style_handler_free (rsvg-base.c:90)
==988==    by 0x4056BB9: rsvg_end_element (rsvg-base.c:681)
==988==    by 0x49C28C1: xmlParseEndTag1 (parser.c:8356)
==988==    by 0x49C9DEB: xmlParseTryOrFinish (parser.c:11154)
==988==    by 0x49CAB24: xmlParseChunk (parser.c:11739)
==988==    by 0x405A238: rsvg_handle_write (rsvg-base.c:1172)