[3.9] bpo-41215: Don't use NULL by default in the PEG parser keyword list (GH-21355) (GH-21356)



(cherry picked from commit 39e76c0fb07e20acad454deb86a0457b279884a9)

Co-authored-by: Pablo Galindo <pablogsal@gmail.com>

Automerge-Triggered-By: @lysnikolaou
diff --git a/Parser/pegen/parse.c b/Parser/pegen/parse.c
index 9d3ac57..d9dd23c 100644
--- a/Parser/pegen/parse.c
+++ b/Parser/pegen/parse.c
@@ -9,8 +9,8 @@
 #endif
 static const int n_keyword_lists = 15;
 static KeywordToken *reserved_keywords[] = {
-    NULL,
-    NULL,
+    (KeywordToken[]) {{NULL, -1}},
+    (KeywordToken[]) {{NULL, -1}},
     (KeywordToken[]) {
         {"if", 510},
         {"in", 518},
@@ -65,11 +65,11 @@
         {"nonlocal", 509},
         {NULL, -1},
     },
-    NULL,
-    NULL,
-    NULL,
-    NULL,
-    NULL,
+    (KeywordToken[]) {{NULL, -1}},
+    (KeywordToken[]) {{NULL, -1}},
+    (KeywordToken[]) {{NULL, -1}},
+    (KeywordToken[]) {{NULL, -1}},
+    (KeywordToken[]) {{NULL, -1}},
     (KeywordToken[]) {
         {"__peg_parser__", 531},
         {NULL, -1},