Rewrite code flow to clarify error handling.

AFNetworking/AFURLResponseSerialization.m

@@ -242,23 +242,28 @@ static id AFJSONObjectByRemovingKeysWithNullValues(id JSONObject, NSJSONReadingO
         }
     }
 
-    id responseObject = nil;
-    NSError *serializationError = nil;
     // Workaround for behavior of Rails to return a single space for `head :ok` (a workaround for a bug in Safari), which is not interpreted as valid input by NSJSONSerialization.
     // See https://github.com/rails/rails/issues/1742
     BOOL isSpace = [data isEqualToData:[NSData dataWithBytes:" " length:1]];
-    if (data.length > 0 && !isSpace) {
-        responseObject = [NSJSONSerialization JSONObjectWithData:data options:self.readingOptions error:&serializationError];
-    } else {
+    
+    if (data.length == 0 || isSpace) {
         return nil;
     }
+    
+    NSError *serializationError = nil;
+    
+    id responseObject = [NSJSONSerialization JSONObjectWithData:data options:self.readingOptions error:&serializationError];
 
-    if (self.removesKeysWithNullValues && responseObject) {
-        responseObject = AFJSONObjectByRemovingKeysWithNullValues(responseObject, self.readingOptions);
+    if (!responseObject)
+    {
+        if (error) {
+            *error = AFErrorWithUnderlyingError(serializationError, *error);
+        }
+        return nil;
     }
-
-    if (error && !responseObject) {
-        *error = AFErrorWithUnderlyingError(serializationError, *error);
+    
+    if (self.removesKeysWithNullValues) {
+        return AFJSONObjectByRemovingKeysWithNullValues(responseObject, self.readingOptions);
     }
 
     return responseObject;
@@ -378,10 +383,14 @@ static id AFJSONObjectByRemovingKeysWithNullValues(id JSONObject, NSJSONReadingO
     NSError *serializationError = nil;
     NSXMLDocument *document = [[NSXMLDocument alloc] initWithData:data options:self.options error:&serializationError];
 
-    if (error && !document) {
-        *error = AFErrorWithUnderlyingError(serializationError, *error);
+    if (!document)
+    {
+        if (error) {
+            *error = AFErrorWithUnderlyingError(serializationError, *error);
+        }
+        return nil;
     }
-
+    
     return document;
 }
 
@@ -458,15 +467,20 @@ static id AFJSONObjectByRemovingKeysWithNullValues(id JSONObject, NSJSONReadingO
         }
     }
 
-    id responseObject;
-    NSError *serializationError = nil;
-
-    if (data) {
-        responseObject = [NSPropertyListSerialization propertyListWithData:data options:self.readOptions format:NULL error:&serializationError];
+    if (!data) {
+        return nil;
     }
-
-    if (error && !responseObject) {
-        *error = AFErrorWithUnderlyingError(serializationError, *error);
+    
+    NSError *serializationError = nil;
+    
+    id responseObject = [NSPropertyListSerialization propertyListWithData:data options:self.readOptions format:NULL error:&serializationError];
+    
+    if (!responseObject)
+    {
+        if (error) {
+            *error = AFErrorWithUnderlyingError(serializationError, *error);
+        }
+        return nil;
     }
 
     return responseObject;