fix: lifecycle

lib/pages/devices_tab_page.dart

@@ -26,8 +26,10 @@ class _DevicesTabPageState extends ConsumerState<DevicesTabPage> {
   static const Duration _bootloaderScanTimeout = Duration(seconds: 10);
 
   StreamSubscription<List<DiscoveredDevice>>? _scanSubscription;
+  BluetoothController? _bluetooth;
   DiscoveredDevice? _dfuDevice;
   bool _isBootloaderScanStarting = false;
+  bool _isDisposed = false;
 
   @override
   void initState() {
@@ -37,8 +39,8 @@ class _DevicesTabPageState extends ConsumerState<DevicesTabPage> {
 
   @override
   void dispose() {
-    final bluetooth = ref.read(bluetoothProvider).valueOrNull;
-    unawaited(_scanSubscription?.cancel());
+    _isDisposed = true;
+    final bluetooth = _bluetooth;
     unawaited(_stopBootloaderScan(bluetooth));
     super.dispose();
   }
@@ -52,14 +54,19 @@ class _DevicesTabPageState extends ConsumerState<DevicesTabPage> {
 
     try {
       final bluetooth = await ref.read(bluetoothProvider.future);
-      if (!mounted) {
+      if (!mounted || _isDisposed) {
         return;
       }
+      _bluetooth = bluetooth;
 
       final scanResult = await bluetooth.startScan(
         timeout: _bootloaderScanTimeout,
         scanMode: ScanMode.lowLatency,
       );
+      if (!mounted || _isDisposed) {
+        await bluetooth.stopScan();
+        return;
+      }
       if (scanResult.isErr()) {
         return;
       }
@@ -74,20 +81,22 @@ class _DevicesTabPageState extends ConsumerState<DevicesTabPage> {
   }
 
   Future<void> _stopBootloaderScan([BluetoothController? bluetooth]) async {
-    await _scanSubscription?.cancel();
+    final subscription = _scanSubscription;
     _scanSubscription = null;
+    await subscription?.cancel();
 
     await bluetooth?.stopScan();
   }
 
   void _updateBootloaderDevice(List<DiscoveredDevice> devices) {
+    if (_isDisposed || !mounted) {
+      return;
+    }
+
     final dfuDevice = devices.cast<DiscoveredDevice?>().firstWhere(
           (device) => device != null && _isBootloaderAdvertisement(device),
           orElse: () => null,
         );
-    if (!mounted) {
-      return;
-    }
 
     if (dfuDevice == null) {
       _clearBootloaderDevice();
@@ -104,7 +113,7 @@ class _DevicesTabPageState extends ConsumerState<DevicesTabPage> {
   }
 
   void _clearBootloaderDevice() {
-    if (!mounted || _dfuDevice == null) {
+    if (_isDisposed || !mounted || _dfuDevice == null) {
       return;
     }
 
@@ -139,12 +148,12 @@ class _DevicesTabPageState extends ConsumerState<DevicesTabPage> {
         builder: (_) => _BootloaderRecoverySetupPage(device: device),
       ),
     );
-    if (!mounted || firmware == null) {
+    if (!mounted || _isDisposed || firmware == null) {
       return;
     }
 
     await _stopBootloaderScan();
-    if (!mounted) {
+    if (!mounted || _isDisposed) {
       return;
     }
     _clearBootloaderDevice();