v1.9.26

• Initializable mixin:
  • ensureInitialized: added onError handler to then call to route errors to _onInitializationError.
  • executeInitializedCallback:
    • Added onError handler to then call on async initialization result to throw InitializationError with stack trace.
  • _FutureExtension:
    • toCompleter: added onError handler to then to complete completer with error and stack trace if not completed.