placeNextCandidates :: LoadSpace -- ^ The used load space
                  -> [ResidualSpace] -- ^ All current residual spaces
                  -> AxeOrder -- ^ A fill order
                  -> EuclideanSpace3D -- ^ A package to be placed
                  -> Quantity -- ^ The package quantity
                  -> Maybe [(ResidualSpace, EuclideanSpace3D, [Vec3])] -- ^ All selections to place at least one package for the next fitting residual space
                                                                    -- (selections in the sense of partial selections of a filled block)
placeNextCandidates _ [] _ _ _ = Nothing
placeNextCandidates :: LoadSpace -- ^ The used load space
                  -> [ResidualSpace] -- ^ All current residual spaces
                  -> AxeOrder -- ^ A fill order
                  -> EuclideanSpace3D -- ^ A package to be placed
                  -> Quantity -- ^ The package quantity
                  -> Maybe [(ResidualSpace, EuclideanSpace3D, [Vec3])]
placeNextCandidates _ [] _ _ _ = Nothing
placeNextCandidates _ [] _ _ _ = Nothing