Bug#635906: Patch for Division by zero in ov_read_filter

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Hi,

I ran into a SIPFPE from libvorbisfile while trying to run FoFiX.
I traced it down to a missing null check.
See attached patch for a fix, that should also fix the bug in Debian BTS.
Thanks!

Greetings
Daniel Exner
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--- libvorbis-1.3.3/lib/vorbisfile.c	2010-10-27 16:54:00.000000000 +0200
+++ libvorbis-1.3.3.new/lib/vorbisfile.c	2012-06-18 22:05:48.000000000 +0200
@@ -1902,7 +1902,8 @@
     long channels=ov_info(vf,-1)->channels;
     long bytespersample=word * channels;
     vorbis_fpu_control fpu;
-    if(samples>length/bytespersample)samples=length/bytespersample;
+    if(bytespersample && samples>length/bytespersample)
+     samples=length/bytespersample;
 
     if(samples <= 0)
       return OV_EINVAL;