Add assertion to rb_gc_impl_writebarrier
We should only be executing WBs when GC is not running. We ran into this issue when debugging 3cd2407045a67838cf2ab949e5164676b6870958.
Add assertion to rb_gc_impl_writebarrier
We should only be executing WBs when GC is not running. We ran into this
issue when debugging 3cd2407045a67838cf2ab949e5164676b6870958.