Removed creation of NSError when a nil URL is downloaded.

@@ -144,13 +144,12 @@ static NSString *const kCompletedCallbackKey = @"completed";
 
 - (void)addProgressCallback:(void (^)(NSUInteger, long long))progressBlock andCompletedBlock:(void (^)(UIImage *, NSData *data, NSError *, BOOL))completedBlock forURL:(NSURL *)url createCallback:(void (^)())createCallback
 {
-    // The URL will be used as the key to the callbacks dictionary so it cannot be nil. If it is nil immediately call the completed block with no image or data and an error.
+    // The URL will be used as the key to the callbacks dictionary so it cannot be nil. If it is nil immediately call the completed block with no image or data.
     if(url == nil)
     {
         if (completedBlock != nil)
         {
-            NSError *error = [NSError errorWithDomain:@"SDWebImageErrorDomain" code:0 userInfo:@{NSLocalizedDescriptionKey: @"Could not load an image because URL was nil."}];
-            completedBlock(nil, nil, error, NO);
+            completedBlock(nil, nil, nil, NO);
         }
         return;
     }