Crash on replaceMetadata:forKey:inCollection with filtered views

[vkovtash]

Hi guys. Thanks for such a nice tool.
I found a strange crash in some cases while using filtered views.
Here some tests to reproduce it https://github.com/vkovtash/YapDbFilteredViewCrash

[robbiehanson]

Many thanks!

I was able to quickly identify the problem thanks to your unit tests. I was also able to copy their design in the official unit tests in order to add test coverage for the offending code paths.