gh-112388: Fix an error that was causing the parser to try to overwrite tokenizer errors (#112410)

Signed-off-by: Pablo Galindo <pablogsal@gmail.com>

Parser/pegen_errors.c

@@ -219,6 +219,10 @@ exit:
 void *
 _PyPegen_raise_error(Parser *p, PyObject *errtype, int use_mark, const char *errmsg, ...)
 {
+    // Bail out if we already have an error set.
+    if (p->error_indicator && PyErr_Occurred()) {
+        return NULL;
+    }
     if (p->fill == 0) {
         va_list va;
         va_start(va, errmsg);