nil scrollview in message VC (#1434)

Author: rnystrom

Local Pods/MessageViewController/MessageViewController/MessageViewController.swift

@@ -80,7 +80,7 @@ open class MessageViewController: UIViewController, MessageAutocompleteControlle
         case hiding
     }
     internal var keyboardState: KeyboardState = .resigned
-    internal var scrollView: UIScrollView!
+    internal var scrollView: UIScrollView?
     internal var keyboardHeight: CGFloat = 0
     internal var isMessageViewHidden = false
 
@@ -104,6 +104,8 @@ open class MessageViewController: UIViewController, MessageAutocompleteControlle
     }
 
     internal func layout() {
+        guard let scrollView = self.scrollView else { return }
+
         let bounds = view.bounds
 
         let safeAreaAdditionalHeight = self.safeAreaAdditionalHeight
@@ -155,21 +157,22 @@ open class MessageViewController: UIViewController, MessageAutocompleteControlle
             let animationDuration = notification.userInfo?[UIKeyboardAnimationDurationUserInfoKey] as? TimeInterval
             else { return }
 
-        scrollView.stopScrolling()
+        scrollView?.stopScrolling()
         keyboardState = .showing
 
         let previousKeyboardHeight = keyboardHeight
         keyboardHeight = keyboardFrame.height
 
         UIView.animate(withDuration: animationDuration) {
+            guard let scrollView = self.scrollView else { return }
             // capture before changing the frame which might have weird side effects
-            let contentOffset = self.scrollView.contentOffset
+            let contentOffset = scrollView.contentOffset
 
             self.layout()
 
-            let scrollViewHeight = self.scrollView.bounds.height
-            let contentHeight = self.scrollView.contentSize.height
-            let topInset = self.scrollView.util_adjustedContentInset.top
+            let scrollViewHeight = scrollView.bounds.height
+            let contentHeight = scrollView.contentSize.height
+            let topInset = scrollView.util_adjustedContentInset.top
             let bottomSafeInset = self.view.util_safeAreaInsets.bottom
 
             let newOffset = max(
@@ -179,7 +182,7 @@ open class MessageViewController: UIViewController, MessageAutocompleteControlle
                 ),
                 -topInset
             )
-            self.scrollView.contentOffset = CGPoint(x: contentOffset.x, y: newOffset)
+            scrollView.contentOffset = CGPoint(x: contentOffset.x, y: newOffset)
         }
     }