textInputbar incorrect position when embeded in a container view

[minuslu]

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Description

As I add a container view(embeds a SLKTextViewController) to a view controller which has tab bar and navigation bar, the textInputbar does not stick on bottom of SLKTextViewController.view

Reproducible in:

• [x] This is reproducible in the sample project. SlackTextViewController version: 1.9.6 iOS version(s): 11.3, 9.3 Device(s): iPhone X Simulator, iPhone 6 Simulator

Steps to reproduce:

1. TabBarController -> NavigationController -> ViewController
2. drag a container view into ViewController
3. embed a SLKTextViewController in container view

Attachments:

e.g. Logs, screenshots, screencast, sample project, funny gif, etc.