investigate index out of bounds in WatchlistVC

[niksauer]

intermediate solution:

guard let currency = displayedCurrencies[safe: indexPath.row] else {
    return false
}
    
return !requiredCurrencies.contains(where: { $0.isEqual(to: currency)})

where [safe:]:

extension Collection where Indices.Iterator.Element == Index {
    subscript (safe index: Index) -> Iterator.Element? {
        return indices.contains(index) ? self[index] : nil
    }
}