BUG/MINOR: backend: check srv_conn before dereferencing it

Commit 3c4e19f42 ("BUG/MEDIUM: backend: always release the previous
connection into its own target srv_list") introduced a valid warning
about a null-deref risk since we didn't check conn_new()'s return value.

This patch must be backported to 1.9 with the patch above.
1 file changed