[ERROR:flutter/lib/ui/dart_runtime_hooks.cc(38)] Dart Error: Unhandled exception: NoSuchMethodError: No top-level getter 'backgroundHandler' declared. Receiver: top-level Tried calling: backgroundHandler #0 NoSuchMethodError._throwNew (dart:core-patch/errors_patch.dart:191) #1 FfiTrampoline___getCallbackFromHandle$Method$FfiNative$Ptr (dart:ffi) #2 _getCallbackFromHandle (dart:ui/natives.dart:11..