Assert should only be used for program internal logic errors, not to sanitize external user input.
The assert was introduced via the debug-only runtime option -checkaddrman in commit 803ef70, thus won't need a backport.
Also, it doesn't really make sense to continue when the deserialized addrman doesn't pass the sanity check.
For example, if nLastSuccess is negative, it would later result in integer overflows.

ninja all check-all