Update Required for Route Class

[adamtmackie]

Hi, thanks for building this template its really good.
The biggest issues that i cannot fix from the latest updates to flutter are generated around the new requirements for classes and onGenerateRoute : (from what i can tell)

1. transferring event data into routes.dart
2. new null safety update which required constructors variables to be set to required (links into problem 1)
3. Upon pressing the AddEvent Button to create an event it fails due to problem 2 same issue is occuring with edit profile button,
   problems beyond these two buttons is unkown as i cant access them.

Note i am using the most up to date versions of each of your dependencies as well as the data from your latest update for flutter_events_2021.

Thankyou in advance

[adamtmackie]

@lohanidamodar