Fixes a problem where viewWillAppear/viewDidAppear/viewWillDisappear/viewDidDisappear will not be called on the child view controllers under certain circumstances:
If the mainViewController is replaced while the drawer is closed
If the drawerViewController is replaced while the drawer is open
Fixes a problem where
viewWillAppear
/viewDidAppear
/viewWillDisappear
/viewDidDisappear
will not be called on the child view controllers under certain circumstances:mainViewController
is replaced while the drawer is closeddrawerViewController
is replaced while the drawer is open