Respond to CR.

// FREEBIE

Signal/src/Models/TSMessageAdapaters/AttachmentUploadView.h

@@ -2,6 +2,8 @@
 //  Copyright (c) 2017 Open Whisper Systems. All rights reserved.
 //
 
+NS_ASSUME_NONNULL_BEGIN
+
 @class TSAttachmentStream;
 
 typedef void (^AttachmentStateBlock)(BOOL isAttachmentReady);
@@ -15,10 +17,10 @@ typedef void (^AttachmentStateBlock)(BOOL isAttachmentReady);
 // * Disable any media view controls using a callback.
 @interface AttachmentUploadView : NSObject
 
-@property (nonatomic, readonly) TSAttachmentStream *attachment;
-
 - (instancetype)initWithAttachment:(TSAttachmentStream *)attachment
                          superview:(UIView *)superview
-           attachmentStateCallback:(AttachmentStateBlock)attachmentStateCallback;
+           attachmentStateCallback:(AttachmentStateBlock _Nullable)attachmentStateCallback;
 
 @end
+
+NS_ASSUME_NONNULL_END

Signal/src/Models/TSMessageAdapaters/AttachmentUploadView.m

@@ -7,6 +7,8 @@
 #import "OWSUploadingService.h"
 #import "TSAttachmentStream.h"
 
+NS_ASSUME_NONNULL_BEGIN
+
 @interface AttachmentUploadView ()
 
 @property (nonatomic) TSAttachmentStream *attachment;
@@ -15,7 +17,7 @@
 
 @property (nonatomic) CALayer *maskLayer;
 
-@property (nonatomic) AttachmentStateBlock attachmentStateCallback;
+@property (nonatomic) AttachmentStateBlock _Nullable attachmentStateCallback;
 
 @property (nonatomic) BOOL isAttachmentReady;
 
@@ -27,7 +29,7 @@
 
 - (instancetype)initWithAttachment:(TSAttachmentStream *)attachment
                          superview:(UIView *)superview
-           attachmentStateCallback:(AttachmentStateBlock)attachmentStateCallback
+           attachmentStateCallback:(AttachmentStateBlock _Nullable)attachmentStateCallback
 {
     self = [super init];
 
@@ -116,3 +118,5 @@
 }
 
 @end
+
+NS_ASSUME_NONNULL_END