Fixes crates getting collected by buildings or other crates

Long overdue fix for a regression I introduced.

Closes #5953. (Or should, it is very hard to test that specific case.)

Based on code from #6159.
(Tested NRE crash case reported in #6159. Buildings no longer collect crates dropped on them.)
This sounds like a word by word translation from German. Are you sure this is valid English? It is also not very explanatory, essentially just repeating the variable name.