don't update the zoom scale or torch state if the camer is not running

@@ -175,9 +175,15 @@ class MobileScannerController extends ValueNotifier<MobileScannerState> {
   }
 
   /// Reset the zoom scale of the camera.
+  ///
+  /// Does nothing if the camera is not running.
   Future<void> resetZoomScale() async {
     _throwIfNotInitialized();
 
+    if (!value.isRunning) {
+      return;
+    }
+
     // When the platform has updated the zoom scale,
     // it will send an update through the zoom scale state event stream.
     await MobileScannerPlatform.instance.resetZoomScale();
@@ -189,9 +195,15 @@ class MobileScannerController extends ValueNotifier<MobileScannerState> {
   ///
   /// If the [zoomScale] is out of range,
   /// it is adjusted to fit within the allowed range.
+  ///
+  /// Does nothing if the camera is not running.
   Future<void> setZoomScale(double zoomScale) async {
     _throwIfNotInitialized();
 
+    if (!value.isRunning) {
+      return;
+    }
+
     final double clampedZoomScale = zoomScale.clamp(0.0, 1.0);
 
     // Update the zoom scale state to the new state.
@@ -313,10 +325,15 @@ class MobileScannerController extends ValueNotifier<MobileScannerState> {
 
   /// Switches the flashlight on or off.
   ///
-  /// Does nothing if the device has no torch.
+  /// Does nothing if the device has no torch,
+  /// or if the camera is not running.
   Future<void> toggleTorch() async {
     _throwIfNotInitialized();
 
+    if (!value.isRunning) {
+      return;
+    }
+
     final TorchState torchState = value.torchState;
 
     if (torchState == TorchState.unavailable) {