Add missing bounds check in ngx_{http,stream}_compile_complex_value()

Complex value compilation scans strings for $1..$9 capture references.
Check that a byte after '$' is present before testing it, matching
ngx_str_t length semantics and avoiding reliance on NUL termination.

Apply the same check to both HTTP and stream implementations.

src/stream/ngx_stream_script.c

@@ -151,7 +151,9 @@ ngx_stream_compile_complex_value(ngx_stream_compile_complex_value_t *ccv)
 
     for (i = 0; i < v->len; i++) {
         if (v->data[i] == '$') {
-            if (v->data[i + 1] >= '1' && v->data[i + 1] <= '9') {
+            if (i + 1 < v->len
+                && v->data[i + 1] >= '1' && v->data[i + 1] <= '9')
+            {
                 nc++;
 
             } else {