BUG/MINOR: log: fix risk of null deref on error path

Previous commit ae32ac74db ("BUG/MINOR: log: fix memory leak on logsrv
parse error") addressed one issue and introduced another one, the logsrv
pointer may also be null at the end of the function so we must test it
before deciding to dereference it.

This should be backported along with the patch above to 2.2.
1 file changed