UI is not responding if awakeFromNib is called twice

I have a project, where SlideMenuController's `awakeFromNib` is called twice during initialization.
Because of this, container views (`mainContainerView`, `leftContainerView`) are creating twice so that the last one is covering the screen making UI inaccessible.

A simple workaround for this could be removing container views before initialization to avoid duplicates:
```
open func initView() {
for subview in view.subviews {
subview.removeFromSuperview()
}

...
```

or, better:
```
open func initView() {
mainContainerView.removeFromSuperview()
opacityView.removeFromSuperview()
leftContainerView.removeFromSuperview()
rightContainerView.removeFromSuperview()

...
```

Start at SlideMenuController's awakeFromNib and initView entry points, then inspect how mainContainerView, leftContainerView, rightContainerView, and opacityView are created. Reproduce the double initialization and ensure the container views are not duplicated or left covering the UI; the issue mentions no specific test file.

Written by the indexing model from the issue text.