Answer:
The error in the sentence is a squinting modifier.
Step-by-step explanation:
The original sentence can be revised as "We kept in the closet an extra rack for the stove", a squinting modifier is a misplaced modifier, this common error creates an ambiguous meaning in the sentence, the original sentence "We kept an extra rack for the stove in the closet." might be understood that the stove is in the closet, while the revised one clearly says that what is in the closet is just the rack.