some fixes

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

@@ -20,7 +20,7 @@ import io.flutter.plugin.common.PluginRegistry
 import io.flutter.plugin.platform.PlatformView
 
 
-class QRView(private val context: Context, messenger: BinaryMessenger, private val id: Int, private val params: HashMap<String, Any>) :
+class QRView(private val context: Context?, messenger: BinaryMessenger, private val id: Int, private val params: HashMap<String, Any>) :
         PlatformView, MethodChannel.MethodCallHandler, PluginRegistry.RequestPermissionsResultListener {
 
     private var isTorchOn: Boolean = false
@@ -279,7 +279,7 @@ class QRView(private val context: Context, messenger: BinaryMessenger, private v
     }
 
     private fun convertDpToPixels(dp: Double) =
-            (dp * context.resources.displayMetrics.density).toInt()
+            (dp * context!!.resources.displayMetrics.density).toInt()
 
     private fun hasCameraPermission(): Boolean {
         return permissionGranted ||

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

@@ -10,7 +10,7 @@ import io.flutter.plugin.platform.PlatformViewFactory
 class QRViewFactory(private val messenger: BinaryMessenger) :
         PlatformViewFactory(StandardMessageCodec.INSTANCE) {
 
-    override fun create(context: Context, id: Int, args: Any?): PlatformView {
+    override fun create(context: Context?, id: Int, args: Any?): PlatformView {
         val params = args as HashMap<String, Any>
         return QRView(context, messenger, id, params)
     }