Remove - while setting collapsed constraints for MessageViewController

[Narek1994]

Sorry for not openning PR, I made a lot of changes, so dont want to push it here :)

private func makeCollapsedConstraints() -> [NSLayoutConstraint] {
    return [
      messageView.bottomAnchor.constraint(equalTo: view.bottomAnchor),
      messageView.leadingAnchor.constraint(equalTo: view.leadingAnchor),
      messageView.trailingAnchor.constraint(equalTo: view.trailingAnchor),
      messageView.heightAnchor.constraint(
        equalToConstant: hideFooterView ? 0 : -BarcodeScannerViewController.footerHeight
      )
    ]
  }

Here I think -BarcodeScannerViewController.footerHeight should be BarcodeScannerViewController.footerHeight height can not be negative.