fix(options): latent codegen bug

Problem:
Latent bug from 7f6c14ed54a46e822b80134d39a89f97523a2706 (2015).
If an option default is "false" (`o.defaults.if_false = false`, e.g.
'fileignorecase'), codegen does not give it a `.def_val` on the platform
where its `#if` condition is undefined; it is zero-initialized.

This wasn't noticed until the parent commit, where zero value is
kObjectTypeNil, which `set_option_varp()` rejects.

Solution:
Check `if_false == nil` insteada of "falsey", so the `#else` branch gets
generated.

0 files changed, 0 insertions, 0 deletions