Fixed aggregation methods of Promise ctor with array-like object.

Previously, while iterating over an array-like object the methods may be
resolved with INVALID values. INVALID value is a special internal type which
should never be visible by ordinary functions.

The fix is to ensure that absent elements are represented by undefined value.

The following methods were fixed Promise.all(), Promise.allSettled(),
    Promise.any(), Promise.race().

This closes #483 issue on Github.

src/njs_promise.c

@@ -1369,6 +1369,10 @@ njs_promise_perform_all_handler(njs_vm_t *vm, njs_iterator_args_t *args,
     njs_promise_all_context_t    *context;
     njs_promise_iterator_args_t  *pargs;
 
+    if (!njs_is_valid(value)) {
+        value = njs_value_arg(&njs_value_undefined);
+    }
+
     pargs = (njs_promise_iterator_args_t *) args;
 
     capability = pargs->capability;
@@ -1459,6 +1463,10 @@ njs_promise_perform_all_settled_handler(njs_vm_t *vm, njs_iterator_args_t *args,
     njs_promise_all_context_t    *context;
     njs_promise_iterator_args_t  *pargs;
 
+    if (!njs_is_valid(value)) {
+        value = njs_value_arg(&njs_value_undefined);
+    }
+
     pargs = (njs_promise_iterator_args_t *) args;
 
     capability = pargs->capability;
@@ -1598,6 +1606,10 @@ njs_promise_perform_any_handler(njs_vm_t *vm, njs_iterator_args_t *args,
     njs_promise_all_context_t    *context;
     njs_promise_iterator_args_t  *pargs;
 
+    if (!njs_is_valid(value)) {
+        value = njs_value_arg(&njs_value_undefined);
+    }
+
     pargs = (njs_promise_iterator_args_t *) args;
 
     capability = pargs->capability;
@@ -1745,6 +1757,10 @@ njs_promise_perform_race_handler(njs_vm_t *vm, njs_iterator_args_t *args,
     njs_promise_capability_t     *capability;
     njs_promise_iterator_args_t  *pargs;
 
+    if (!njs_is_valid(value)) {
+        value = njs_value_arg(&njs_value_undefined);
+    }
+
     pargs = (njs_promise_iterator_args_t *) args;
 
     ret = njs_function_call(vm, pargs->function, pargs->constructor, value,

src/test/njs_unit_test.c

@@ -21149,6 +21149,13 @@ static njs_unit_test_t  njs_externals_test[] =
               "}))"
               ".then(v => $r.retval(v))"),
       njs_str("a:async:pr:async2:pr:r,b:async:pr:async2:pr:r,c:async:pr:async2:pr:r") },
+
+    { njs_str("async function f () {"
+              "    var p = await Promise.race({length:1});"
+              "    for (const v in 'test') { }"
+              "};"
+              "f().then(v => $r.retval('done'))"),
+      njs_str("done") },
 };