Null safety support

[EnderXenocida]

Error: Cannot run with sound null safety, because the following dependencies
don't support null safety:

 - package:dart_mercure
 - package:eventsource
 - package:http
 - package:http_parser

[BilguunTs]

Yea, since it doesn't support null safety you should run with flutter run [iOS or android] --no-sound-null-safety same with build command.