test zero value in an "if" directive consistently with predicates fixed in r3894
thanks to Maxim Dounin

src/http/ngx_http_script.c

diff --git a/src/http/ngx_http_script.c b/src/http/ngx_http_script.c
index 7c8de14..a703f08 100644
--- a/src/http/ngx_http_script.c
+++ b/src/http/ngx_http_script.c
@@ -1395,7 +1395,7 @@
 
     e->sp--;
 
-    if (e->sp->len && e->sp->data[0] != '0') {
+    if (e->sp->len && (e->sp->len !=1 || e->sp->data[0] != '0')) {
         if (code->loc_conf) {
             e->request->loc_conf = code->loc_conf;
             ngx_http_update_location_config(e->request);