Unterminated JSON strings are misleadingly reported as “Control character error”

### Description The following code: ```php <?php var_dump(json_decode('"'), json_last_error_msg()); ``` Resulted in this output: ``` NULL string(53) "Control character error, possibly incorrectly encoded" ``` But I expected this output instead: Something about EOF being reached. ### PHP Version ```plain PHP 8.5.7 (cli) (built: Jun 6 2026 05:36:56) (NTS) Copyright (c) The PHP Group Built by Ubuntu Zend Engine v4.5.7, Copyright (c) Zend Technologies with Zend OPcache v8.5.7, Copyright (c), by Zend Technologies ``` ### Operating System _No response_