Try to assert(0) less vigorously

The recent assert_no_tls_errors() -> check_no_tls_errors() patch makes me worry that there could be other places where we bail out of our code too aggressively. We should go through our asserts and see if there are any places where we assert(0) that we could recover from instead.

[Automatically added by flyspray2trac: Operating System: All]