Updated nullability for Swift. (#509)

Author: E-B-Smith

Branch-SDK/Branch-SDK/BNCCallbacks.h

@@ -11,11 +11,11 @@
 
 @class BranchUniversalObject, BranchLinkProperties;
 
-typedef void (^callbackWithParams) (NSDictionary * _Nonnull params, NSError * _Nullable error);
-typedef void (^callbackWithUrl) (NSString * _Nonnull url, NSError * _Nullable error);
+typedef void (^callbackWithParams) (NSDictionary * _Nullable params, NSError * _Nullable error);
+typedef void (^callbackWithUrl) (NSString * _Nullable url, NSError * _Nullable error);
 typedef void (^callbackWithStatus) (BOOL changed, NSError * _Nullable error);
 typedef void (^callbackWithList) (NSArray * _Nullable list, NSError * _Nullable error);
 typedef void (^callbackWithUrlAndSpotlightIdentifier) (NSString * _Nullable url, NSString * _Nullable spotlightIdentifier, NSError * _Nullable error);
-typedef void (^callbackWithBranchUniversalObject) (BranchUniversalObject * _Nonnull universalObject, BranchLinkProperties * _Nonnull linkProperties, NSError * _Nullable error);
+typedef void (^callbackWithBranchUniversalObject) (BranchUniversalObject * _Nullable universalObject, BranchLinkProperties * _Nullable linkProperties, NSError * _Nullable error);
 
 #endif /* BNCCallbacks_h */