Thread Exception Handeling Issue FIX

I was getting an exception from Thread and was not able to catch. I
applied a fix.

Exception
java.nio.ReadOnlyBufferException
at java.nio.DirectByteBufferR.putInt(DirectByteBufferR.java:708)
at
com.sun.pdfview.font.ttf.TrueTypeFont.calculateChecksum(TrueTypeFont.jav
a:262)
Merge pull request #22 from smntb/master

Thread Exception Handeling Issue FIX