The issue is that the new keyword `force_lease_closed` was being set
even if the user didn't specify it, which results in breakage if this
new pyln version talks to older c-lightning nodes that don't have this
keyword yet. By setting the default to `None` it gets filtered out if
the user has not explicitly set it, but still retains the `True` /
`False` values if they did.
Changelog-None Issue is not present in released versions
d732fa9724