Tiny bug fix in engine_marktask()
In engine_marktask() only check whether to rebuild the space for density pair/sub-pair, not for all sub-types of pair/sub-pair. Leads to problems with mixed gravity/hydro runs otherwise.
In engine_marktask() only check whether to rebuild the space for density pair/sub-pair, not for all sub-types of pair/sub-pair. Leads to problems with mixed gravity/hydro runs otherwise.
