Fixed problem sending nested arrays in formData with mime attachments

I've had problems sending a request with 

        multipartFormRequestWithMethod:(NSString *)method
             					  path:(NSString *)path
							parameters:(NSDictionary *)parameters
			 constructingBodyWithBlock:(void (^)(id <AFMultipartFormData> formData))block
          

I have a server that expected to receive a post param this way:

	comment_attributes[0][some_other_key] 

and was sending:

	comment_attributes[][some_other_key].

Now it works for me but please let me know if I have to change something in another file and I'll do it.