Eu literalmente peguei o codigo do professor e rodei na minha maquina e continuou dando o mesmo erro que estava anteriormente erro :
E/flutter ( 5363): [ERROR:flutter/lib/ui/ui_dart_state.cc(209)] Unhandled Exception: Unsupported operation: Cannot add to a fixed-length list
E/flutter ( 5363): #0 FixedLengthListMixin.add (dart:_internal/list.dart:21:5)
E/flutter ( 5363): #1 findAll.<anonymous closure>.<anonymous closure> (package:lista_tarefas/database/app_database.dart:36:18)
E/flutter ( 5363): #2 _rootRunUnary (dart:async/zone.dart:1434:47)
E/flutter ( 5363): #3 _CustomZone.runUnary (dart:async/zone.dart:1335:19)
E/flutter ( 5363): <asynchronous suspension>
E/flutter ( 5363):
