release camera when widget dispose

android/src/main/kotlin/net/touchcapture/qr/flutterqr/QRView.kt

@@ -88,6 +88,7 @@ class QRView(context: Context, private val registrar: PluginRegistry.Registrar,
     }
 
     override fun dispose() {
+        barcodeView.pause()
     }
 
     private inner class CameraRequestPermissionsListener : PluginRegistry.RequestPermissionsResultListener {
@@ -143,4 +144,4 @@ class QRView(context: Context, private val registrar: PluginRegistry.Registrar,
         }
     }
 
-}
+}