NSLayoutConstraint error when using expandable input and switching input

Reproducible with the demo app, using the "Chat with expandable input" example.

**Steps to reproduce:**
1. Press the keyboard chat input icon.
2. Press the camera chat input icon.

The console will show the following error:
```
2019-05-22 10:55:34.230615-0400 ChattoApp[3658:2922342] [LayoutConstraints] Unable to simultaneously satisfy constraints.
Probably at least one of the constraints in the following list is one you don't want.
Try this:
(1) look at each constraint and try to figure out which you don't expect;
(2) find the code that added the unwanted constraint or constraints and fix it.
(
"<_UILayoutSupportConstraint:0x2814a9f90 _UILayoutSpacer:0x2808e9e00'UIVC-topLayoutGuide'.height == 64 (active)>",
"<_UILayoutSupportConstraint:0x2814a9810 V:|-(0)-[_UILayoutSpacer:0x2808e9e00'UIVC-topLayoutGuide'] (active, names: '|':Chatto.BaseChatViewControllerView:0x101c64670 )>",
"",
"",
"",
"",
"",
"",
"=0)-[UIView:0x101ca67e0] (active)>",
""
)

Will attempt to recover by breaking constraint

Make a symbolic breakpoint at UIViewAlertForUnsatisfiableConstraints to catch this in the debugger.
The methods in the UIConstraintBasedLayoutDebugging category on UIView listed in may also be helpful.
2019-05-22 10:55:34.243398-0400 ChattoApp[3658:2922342] [LayoutConstraints] Unable to simultaneously satisfy constraints.
Probably at least one of the constraints in the following list is one you don't want.
Try this:
(1) look at each constraint and try to figure out which you don't expect;
(2) find the code that added the unwanted constraint or constraints and fix it.
(
"<_UILayoutSupportConstraint:0x2814a9f90 _UILayoutSpacer:0x2808e9e00'UIVC-topLayoutGuide'.height == 64 (active)>",
"<_UILayoutSupportConstraint:0x2814a9810 V:|-(0)-[_UILayoutSpacer:0x2808e9e00'UIVC-topLayoutGuide'] (active, names: '|':Chatto.BaseChatViewControllerView:0x101c64670 )>",
"=0)-[UIView:0x101ca67e0] (active)>",
"",
""
)

Will attempt to recover by breaking constraint
=0)-[UIView:0x101ca67e0] (active)>
```

Run the demo app and open the “Chat with expandable input” example. Reproduce the issue by pressing the keyboard chat input icon and then the camera chat input icon, then inspect the reported NSLayoutConstraint warnings. Done means switching inputs no longer produces unsatisfiable-constraint errors.

Written by the indexing model from the issue text.