[3.7] bpo-34492: Modules/main.c: Fix copy_wstrlist() (GH-8910) (GH-8922)

* Add missing NULL check reported by Svace static analyzer.
* Fix clear_wstrlist() call on a wrong list.

(cherry picked from commit eb746db)

Co-authored-by: Alexey Izbyshev <[email protected]>

Author: Alexey Izbyshev

Modules/main.c

@@ -1236,10 +1236,13 @@ copy_wstrlist(int len, wchar_t **list)
     assert((len > 0 && list != NULL) || len == 0);
     size_t size = len * sizeof(list[0]);
     wchar_t **list_copy = PyMem_RawMalloc(size);
+    if (list_copy == NULL) {
+        return NULL;
+    }
     for (int i=0; i < len; i++) {
         wchar_t* arg = _PyMem_RawWcsdup(list[i]);
         if (arg == NULL) {
-            clear_wstrlist(i, list);
+            clear_wstrlist(i, list_copy);
             return NULL;
         }
         list_copy[i] = arg;