Use best-effort mode for sb-debug:print-backtrace
Use best-effort mode for sb-debug:print-backtrace

When :emergency-best-effort is set to t in sb-debug:print-backtrace,
that logic attempts to print as much of the backtrace as possible,
even when it encounters errors printing individual frames or objects.

That logic was added to SBCL in February 2014:
https://github.com/sbcl/sbcl/commit/fb51ab

gwkkwg/trivial-backtrace