Do not stop building the metrics file if the unicode index is not found for a kerning entry. In my tests with OpenType fonts provided with Ubuntu, this happened quite often, probably  caused by extraneous kerning entries which do not point to valid glyphs.
Do not stop building the metrics file if the unicode index is not found for a kerning entry.
In my tests with OpenType fonts provided with Ubuntu, this happened quite often, probably 
caused by extraneous kerning entries which do not point to valid glyphs.

git-svn-id: 102839466c3b40dd9c7e25c0a1a6d26afc40150a@463581 13f79535-47bb-0310-9956-ffa450edef68

chunlinyao/fop,chunlinyao/fop,apache/fop,chunlinyao/fop,apache/fop,chunlinyao/fop,apache/fop,apache/fop,chunlinyao/fop,apache/fop