Add nullability annotations to newer APIs that lacked it from the original PR.

Author: Scott Goodson

AsyncDisplayKit-Prefix.gcda

@@ -27,7 +27,7 @@ typedef UIView * _Nonnull(^ASDisplayNodeViewBlock)();
 /**
  * UIView creation block. Used to create the backing view of a new display node.
  */
-typedef UIViewController *(^ASDisplayNodeViewControllerBlock)();
+typedef UIViewController * _Nonnull(^ASDisplayNodeViewControllerBlock)();
 
 /**
  * CALayer creation block. Used to create the backing layer of a new display node.

AsyncDisplayKit/ASDisplayNode.h

@@ -361,9 +361,7 @@ NS_ASSUME_NONNULL_BEGIN
 
 @end
 
-<<<<<<< HEAD
-NS_ASSUME_NONNULL_END
-=======
-@protocol ASTableViewDelegate <ASTableDelegate>;
+@protocol ASTableViewDelegate <ASTableDelegate>
 @end
->>>>>>> master
+
+NS_ASSUME_NONNULL_END

AsyncDisplayKit/ASTableView.h

@@ -18,12 +18,14 @@ @implementation ASViewController
 
 - (instancetype)initWithNibName:(NSString *)nibNameOrNil bundle:(NSBundle *)nibBundleOrNil
 {
-  return [self initWithNode:nil];
+  ASDisplayNodeAssert(NO, @"ASViewController requires using -initWithNode:");
+  return [self initWithNode:[[ASDisplayNode alloc] init]];
 }
 
 - (instancetype)initWithCoder:(NSCoder *)aDecoder
 {
-  return [self initWithNode:nil];
+  ASDisplayNodeAssert(NO, @"ASViewController requires using -initWithNode:");
+  return [self initWithNode:[[ASDisplayNode alloc] init]];
 }
 
 - (instancetype)initWithNode:(ASDisplayNode *)node