https://github.com/zeek/zeek/issues/5557

In C++20 which we use assert is still a mess since it is so
underspecified, but many implementations already perform
conversion of its arguments to bool; this is likely the reason
we missed this. According to your logs the implementation of
assert in your particular build configuration does not do that

https://github.com/zeek/spicy/pull/2399
Do not assume assert performs C++26 contextual conversions

(plus two additional changes)