[__NSPlaceholderDictionary initWithObjects:forKeys:count:]: attempt to insert nil object from objects[1]'
NSDictionary創建有兩種方法，NSDictionary *dic =@{@"xxx":@"xxx"}；或者NSDictionary *dic =[NSDictionary dictionaryWithObjectsAndKeys:@"xxx",@"xxx",nil];但是用第一種創建的dic里面的元素一定不能為空，否則就會崩潰。。。
