Fix issue where loading lightning field from weather save file might trigger a crash.
Loop to make sure crates have content, or change them to open crates if no items have been placed.
Destroy crates when no items have been spawned in it.
Merge branch 'fix-lightning-crash-maybe' of https://github.com/kevingranade/Cataclysm-DDA into two
Merge branch 'make-crates-spwan-full' of https://github.com/BevapDin/Cataclysm-DDA into two
Merge branch 'two'