Fix a bug in writebuf_output which caused the process to crash if apr_file_write returned an error, because count can be 0 and conn->block_handler can be NULL => BOOM!
Fix a bug in writebuf_output which caused the process to crash if
apr_file_write returned an error, because count can be 0 and
conn->block_handler can be NULL => BOOM!

This most likely fixed a bunch of cases where the repository would
need recovery when it was accessed via ra_svn.

It is also likely that this fixes issue #1626 (win32 svnserve
exits on protocol error).

* subversion/libsvn_ra_svn/marshal.c

  (writebuf_output): Check for error before looking at count.

jmckaskill/subversion,jmckaskill/subversion,jmckaskill/subversion,jmckaskill/subversion,jmckaskill/subversion,jmckaskill/subversion,jmckaskill/subversion,jmckaskill/subversion