fix up find_inside
fix up find_inside

It didn't work for arrays or hashes nested more than two deep, thanks
Naklion.

See https://github.com/libvips/ruby-vips/commit/22cc689663478f02b611a837a8b6992c7dbb8b48#r36237633

jcupitt/ruby-vips,jcupitt/ruby-vips