tor-chanmgr: remove panics in debug builds

These were supposed to fail loudly in debug builds by panicking, but panics are mostly useless for debugging in async applications that use a runtime which catches panics. So we'll just log the error instead.

One of these panics actually occurs often in practice (see #1716 (closed) and #1731).

assigned to @opara

requested review from @ahf

approved this merge request

Looks good. Let's get this in. Merging since the error seems unrelated to this.

merged

mentioned in commit 69125b90

mentioned in issue #1731

mentioned in issue #1716 (closed)

mentioned in issue #1780