Remove a needless check in channel_tls_handle_incoming

This patch removes an "if (chan)" that occurred at a place where
chan was definitely non-NULL.  Having it there made some static
analysis tools conclude that we were up to shenanigans.

This resolves #9979.

src/or/channeltls.c

@@ -287,8 +287,8 @@ channel_tls_handle_incoming(or_connection_t *orconn)
   if (is_local_addr(&(TO_CONN(orconn)->addr))) channel_mark_local(chan);
   channel_mark_incoming(chan);
 
-  /* If we got one, we should register it */
-  if (chan) channel_register(chan);
+  /* Register it */
+  channel_register(chan);
 
   return chan;
 }