Add null statement

parse.c

@@ -91,8 +91,13 @@ static Node *compound_stmt(Token **rest, Token *tok) {
   return node;
 }
 
-// expr-stmt = expr ";"
+// expr-stmt = expr? ";"
 static Node *expr_stmt(Token **rest, Token *tok) {
+  if (equal(tok, ";")) {
+    *rest = tok->next;
+    return new_node(ND_BLOCK);
+  }
+
   Node *node = new_unary(ND_EXPR_STMT, expr(&tok, tok));
   *rest = skip(tok, ";");
   return node;

test.sh

@@ -60,5 +60,6 @@ assert 2 '{ 1; return 2; 3; }'
 assert 3 '{ 1; 2; return 3; }'
 
 assert 3 '{ {1; {2;} return 3;} }'
+assert 5 '{ ;;; return 5; }'
 
 echo OK