r1380608 breaks svnsync

Hi Stefan,

For some reason, this commit causes the forked process
executing the pre-revprop-change script to segfault under
certain circumstances.

My reproduction recipe script under x64 Ubuntu 12.10:

[[[
#!/bin/sh
./autogen.sh
./configure --disable-shared --enable-maintainer-mode --without-berkeley-db
make -sj

./subversion/svnadmin/svnadmin create /dev/shm/test_repo
--pre-1.6-compatible
printf "#!/bin/sh\nexit 0\n" > /dev/shm/test_repo/hooks/pre-revprop-change
chmod +x /dev/shm/test_repo/hooks/pre-revprop-change

./subversion/svnsync/svnsync init file:///dev/shm/test_repo/
http://svn.apache.org/repos/asf
./subversion/svnsync/svnsync sync file:///dev/shm/test_repo/
]]]

This crashes for me reliably at rev 80 but YMMV.

-- Stefan^2.

-- 
Certified & Supported Apache Subversion Downloads:
*
http://www.wandisco.com/subversion/download
*