Fix obstructed entities being able to drop off resources.
Introduced in r25215 / rP25215 by not checking the range anymore.
Reported by @FFFF at https://wildfiregames.com/forum/topic/72985-stuck-units-delivering-resourses/.
Differential revision: https://code.wildfiregames.com/D4531
Tested by: @Langbart
Fixes #6446