PDFBOX-2423: Improve pattern rendering

git-svn-id: https://svn.apache.org/repos/asf/pdfbox/trunk@1643042 13f79535-47bb-0310-9956-ffa450edef68
PDFBOX-2540: avoid ArrayIndexOutOfBoundsException if font is empty

git-svn-id: https://svn.apache.org/repos/asf/pdfbox/trunk@1643161 13f79535-47bb-0310-9956-ffa450edef68