gh-95355: Check tokens[0] after allocating memory (GH-95356)

#95355

Automerge-Triggered-By: GH:pablogsal

Misc/NEWS.d/next/Core and Builtins/2022-07-28-08-33-31.gh-issue-95355.yN4XVk.rst

+``_PyPegen_Parser_New`` now properly detects token memory allocation errors. Patch by Honglin Zhu.

Parser/pegen.c

@@ -738,7 +738,7 @@ _PyPegen_Parser_New(struct tok_state *tok, int start_rule, int flags,
         return (Parser *) PyErr_NoMemory();
     }
     p->tokens[0] = PyMem_Calloc(1, sizeof(Token));
-    if (!p->tokens) {
+    if (!p->tokens[0]) {
         PyMem_Free(p->tokens);
         PyMem_Free(p);
         return (Parser *) PyErr_NoMemory();