Null safety

[cuong292]

Hi guys, Thanks for your hard work to create a wonderful Plugins for Dart. I have an idea for better null safety that in fromJson method we should check like map['data'] == null ? [] : List.from... map['data'] == null ? null : Data.fromJson... So it not error while data might be null Also for null safety, all Object should be null able.

I tried to make a local plugin but fail, so i create this issue and hope it can be updated soon

Many thanks