(Heisen)segfault on Julia 1.6, x86 macOS

[odow]

The last build on master segfaulted on Julia 1.6 and macOS:
https://github.com/jump-dev/Cbc.jl/runs/6280862905?check_suite_focus=true
but the PR from which it came didn't:
https://github.com/jump-dev/Cbc.jl/runs/6280640822?check_suite_focus=true

I just triggered it locally, but now I can't reproduce.

[odow]

Closing as non-reproducible.

[odow]

This is still a problem. x-ref #222

[odow]

Closing as duplicate of #187