Maintain end-of-input sentinel in reset_tokens()

Trunk's WP_MySQL_Parser::reset_tokens() lets the parser be reused across
queries by swapping in a new token array. The performance branch's parser
relies on an end-of-input sentinel token (id = EMPTY_RULE_ID) appended at
$tokens[$token_count] so the hot path can read $tokens[$pos]->id without
a range check; reset_tokens() must reproduce that invariant or the next
parse() walks off the end.

Append the sentinel and update $token_count in reset_tokens(), matching
WP_Parser::__construct().

Author: JanJakes

packages/mysql-on-sqlite/src/mysql/class-wp-mysql-parser.php

@@ -14,6 +14,10 @@ class WP_MySQL_Parser extends WP_Parser {
 	 * @param array<WP_Parser_Token> $tokens The parser tokens.
 	 */
 	public function reset_tokens( array $tokens ): void {
+		$this->token_count = count( $tokens );
+		// Maintain the end-of-input sentinel that parse_recursive() relies on.
+		// See WP_Parser::__construct for the invariants.
+		$tokens[]          = new WP_Parser_Token( WP_Parser_Grammar::EMPTY_RULE_ID, 0, 0, '' );
 		$this->tokens      = $tokens;
 		$this->position    = 0;
 		$this->current_ast = null;