Hi @qq2094629698 and welcome to WordPress Trac! I did a search for this specific report, and I cannot find one that matches up exactly. So, thank you for reporting this! I am updating the ticket details for better discoverability for other contributors and users who may experience the same issue.
Tracing this in the 6.0 branch, this seems to point to https://core.trac.wordpress.org/browser/branches/6.0/src/wp-includes/formatting.php#L3415 which does implement count on a variable that could indeed be false.
Paging @jrf to see if this should be treated any differently than other type validation fixes(e.g. #54827) or attempt to track down at the source of where convert_smilies is being called.
If this requires a similar solution to #54827, we can also tag this with good-first-bug and needs-patch.