This can trigger a crash because we assume we
can supply null ptrs and undefined values for
values of those types, as we should be treated
them as zero-size.
Interestingly, this crash only shows up (atm)
in non-optimized builds. Therefore, I added
a -Z no-opt flag so that the new test
(capture_nil) can specify that it should not
run with optimizations enabled.
This should address the valgrind failure that @elliotslaughter
was seeing, though I am not sure why the bots / test continued
to pass, since this is precisely the condition this test was looking
for!
