handle camera permission error in the controller

@@ -159,14 +159,23 @@ class MobileScannerController {
           .values[await _methodChannel.invokeMethod('state') as int? ?? 0];
       switch (state) {
         case MobileScannerState.undetermined:
+          try {
             final bool result =
                 await _methodChannel.invokeMethod('request') as bool? ?? false;
+
             if (!result) {
-            isStarting = false;
               throw const MobileScannerException(
                 errorCode: MobileScannerErrorCode.permissionDenied,
               );
             }
+          } catch (error) {
+            throw const MobileScannerException(
+              errorCode: MobileScannerErrorCode.genericError,
+            );
+          } finally {
+            isStarting = false;
+          }
+
           break;
         case MobileScannerState.denied:
           isStarting = false;