Window management issues on MacOS

[pschuegr]

When using the "Show Modal Dialog" or "Show Other Windows" on MacOS (M1), the log prints the following and hangs:

[ERROR:flutter/runtime/dart_vm_initializer.cc(41)] Unhandled Exception: PlatformException(Value(Message("missing field `alwaysOnTop`")), missing field `alwaysOnTop`, null, null)
#0      WindowMethodDispatcher.invokeMethod (package:nativeshell/src/window_method_channel.dart:71:7)
<asynchronous suspension>
#1      OtherWindowState.initializeWindow (package:nativeshell_examples/pages/other_window.dart:28:5)
<asynchronous suspension>
#2      _prepareAndShow (package:nativeshell/src/window_widget.dart:462:3)
<asynchronous suspension>

Haven't had a chance to look into it any farther yet.