simplified code across the app and consolidated duplicated helpers

lib/widget/async_actions/async_mixin.dart

@@ -23,15 +23,13 @@ class _AsyncMixin extends StatefulWidget {
 }
 
 class _AsyncMixinState extends State<_AsyncMixin> {
-  late final AsyncActionController _internal;
-  AsyncActionController get _controller => widget.controller ?? _internal;
+  AsyncActionController? _own;
+  AsyncActionController get _controller =>
+      widget.controller ?? (_own ??= AsyncActionController());
 
   @override
   void initState() {
     super.initState();
-    if (widget.controller == null) {
-      _internal = AsyncActionController();
-    }
     _controller.addListener(_onControllerChange);
   }
 
@@ -39,7 +37,7 @@ class _AsyncMixinState extends State<_AsyncMixin> {
   void didUpdateWidget(covariant _AsyncMixin oldWidget) {
     super.didUpdateWidget(oldWidget);
     if (oldWidget.controller != widget.controller) {
-      (oldWidget.controller ?? _internal).removeListener(_onControllerChange);
+      (oldWidget.controller ?? _own)?.removeListener(_onControllerChange);
       _controller.addListener(_onControllerChange);
     }
   }
@@ -47,9 +45,7 @@ class _AsyncMixinState extends State<_AsyncMixin> {
   @override
   void dispose() {
     _controller.removeListener(_onControllerChange);
-    if (widget.controller == null) {
-      _internal.dispose();
-    }
+    _own?.dispose();
     super.dispose();
   }
 
@@ -76,11 +72,11 @@ class _AsyncMixinState extends State<_AsyncMixin> {
 
   @override
   Widget build(BuildContext context) {
-    final handler = widget.onPressed == null ? null : _trigger;
+    final busy = _controller.busy;
     return widget.builder(
       context,
-      _controller.busy,
-      _controller.busy ? null : handler,
+      busy,
+      busy || widget.onPressed == null ? null : _trigger,
     );
   }
 }