PDF-725 added a check to make sure a xref table is valid before adding it to a xref chain.

git-svn-id: http://anonsvn.icesoft.org/repo/icepdf/trunk/icepdf@40444 8668f098-c06c-11db-ba21-f49e70c34f74
PDF-729 fixed NaN return value when encountering a negative input.

git-svn-id: http://anonsvn.icesoft.org/repo/icepdf/trunk/icepdf@40445 8668f098-c06c-11db-ba21-f49e70c34f74
PDF-723 added code protection for malformed scn token.

git-svn-id: http://anonsvn.icesoft.org/repo/icepdf/trunk/icepdf@40447 8668f098-c06c-11db-ba21-f49e70c34f74