Missing section identifier in UICollectionViewDelegate methods when deleting sections

[absoftware]

Checklist

• [YES] Reviewed the README and documents.
• [YES] Searched existing issues for ensure not duplicated.

Description

When it's called just after applying deleted section

    func collectionView(_ collectionView: UICollectionView, layout collectionViewLayout: UICollectionViewLayout, insetForSectionAt section: Int) -> UIEdgeInsets {

        // it crashes when it's called just after applying deleted section
        let sectionIdentifier1 = self.dataSource.snapshot().sectionIdentifiers[section]

        // it would be nice to have sth like this as data source is still correct when snapshot actually isn't
        let sectionIdentifier2 = self.dataSource.sectionIdentifier(for: section) 

        // I need to know which section is here
    }

then it crashes or it's not possible to get section identifier in UICollectionViewDelegate methods.

[absoftware]

I reported PR for this: #34