Update lib/src/mobile_scanner.dart

Co-authored-by: Navaron Bracke <brackenavaron@gmail.com>

@@ -285,7 +285,23 @@ class _MobileScannerState extends State<MobileScanner>
   }
   }
 
 
   Future<void> disposeMobileScanner() async {
   Future<void> disposeMobileScanner() async {
+  Future<void> disposeMobileScanner() async {
+    if (widget.controller == null) {
+      WidgetsBinding.instance.removeObserver(this);
+    }
+  
     await _subscription?.cancel();
     await _subscription?.cancel();
+    _subscription = null;
+    
+    if (controller.autoStart) {
+      await controller.stop();
+    }
+    
+    // Dispose default controller if not provided by user
+    if (widget.controller == null) {
+      await controller.dispose();
+    }    
+  }
     WidgetsBinding.instance.removeObserver(this);
     WidgetsBinding.instance.removeObserver(this);
 
 
     if (controller.autoStart) {
     if (controller.autoStart) {