CLEANUP: fcgi-app; Remove useless assignment to NULL

When the fcgi configuration is checked and fcgi rules are created, a useless
assignment to NULL is reported by Covertiy. Let's remove it.

This patch should fix the coverity report #2161.
diff --git a/src/fcgi-app.c b/src/fcgi-app.c
index e0f3232..16c3c81 100644
--- a/src/fcgi-app.c
+++ b/src/fcgi-app.c
@@ -270,7 +270,6 @@
 			LIST_APPEND(&fcgi_conf->param_rules, &rule->list);
 		else /* FCGI_RULE_PASS_HDR/FCGI_RULE_HIDE_HDR */
 			LIST_APPEND(&fcgi_conf->hdr_rules, &rule->list);
-		rule = NULL;
 	}
 	return 0;