Blank lines cause failure

[GoogleCodeExporter]

What steps will reproduce the problem?
1. include a blank line in \digraph[...]{...}{ here }
2. compile with pdflatex

What is the expected output? What do you see instead?
Should produce the same as if the blank line was not there, but instead 
compilation fails.

What version of the product are you using? On what operating system?
> latex --version
pdfTeX 3.1415926-2.4-1.40.13 (TeX Live 2012/Debian)
kpathsea version 6.1.0
Compiled with libpng 1.2.49; using libpng 1.2.49
Compiled with zlib 1.2.7; using zlib 1.2.7
Compiled with poppler version 0.20.4

and TexMaker 3.4
on Linux Mint 14 Nadia, Kernel: Linux 3.5.0-39-generic (x86_64)

Original issue reported on code.google.com by Synei...@gmail.com on 18 Sep 2013 at 1:12