fix directory test in try_files

src/http/ngx_http_core_module.c

diff --git a/src/http/ngx_http_core_module.c b/src/http/ngx_http_core_module.c
index beb0666..4350ab1 100644
--- a/src/http/ngx_http_core_module.c
+++ b/src/http/ngx_http_core_module.c
@@ -3956,6 +3956,7 @@
         if (tf[i].name.data[tf[i].name.len - 1] == '/') {
             tf[i].test_dir = 1;
             tf[i].name.len--;
+            tf[i].name.data[tf[i].name.len] = '\0';
         }
 
         n = ngx_http_script_variables_count(&tf[i].name);