Constraints problem when adding DemoChatViewController as a child view controller

I am trying to add DemoChatViewController(subclass of BaseChatViewController) into a view as a child view controller:

addChildViewController(child)
child.view.translatesAutoresizingMaskIntoConstraints = false
view.addSubview(child.view)
child.didMove(toParentViewController: self)

view.addConstraints([
NSLayoutConstraint(item: child.view, attribute: .top, relatedBy: .equal, toItem: view, attribute: .top, multiplier: 1, constant: 0),
NSLayoutConstraint(item: child.view, attribute: .bottom, relatedBy: .equal, toItem: view, attribute: .bottom, multiplier: 1, constant: 0),
NSLayoutConstraint(item: child.view, attribute: .leading, relatedBy: .equal, toItem: view, attribute: .leading, multiplier: 1, constant: 0),
NSLayoutConstraint(item: child.view, attribute: .trailing, relatedBy: .equal, toItem: view, attribute: .trailing, multiplier: 1, constant: 0)
])

But I got runtime error: Unable to simultaneously satisfy constraints.
"<_UILayoutSupportConstraint:0x600000285960 _UILayoutSpacer:0x6000005cce40'UIVC-topLayoutGuide'.height == 0 (active)>",
"<_UILayoutSupportConstraint:0x600000284f60 V:|-(0)-[_UILayoutSpacer:0x6000005cce40'UIVC-topLayoutGuide'] (active, names: '|':Chatto.BaseChatViewControllerView:0x7fa67342a940 )>",
"",
"",
"=0)-[UIView:0x7fa66df6f110] (active)>",
"",
"",
"",
"",
"",
"",
"",
"",
"",
"",
""
)

Will attempt to recover by breaking constraint

Any suggestion? Thanks in advance.
Cheers