Fix class

library/src/main/java/com/frostnerd/dnstunnelproxy/NoConnectionDnsHandle.kt

@@ -58,13 +58,13 @@ class NoConnectionDnsHandle(
         val request = NetworkRequest.Builder().addCapability(NetworkCapabilities.NET_CAPABILITY_NOT_VPN).build()
         synchronized(this) {
             networkCallback = object:ConnectivityManager.NetworkCallback() {
-                override fun onAvailable(network: Network?) {
+                override fun onAvailable(network: Network) {
                     super.onAvailable(network)
                     packetProxy.tunnelHandle?.proxy?.logger?.info { "[NoConnectionDnsHandle] Network $network became available" }
                     handleChange(network)
                 }
 
-                override fun onLost(network: Network?) {
+                override fun onLost(network: Network) {
                     super.onLost(network)
                     packetProxy.tunnelHandle?.proxy?.logger?.info { "[NoConnectionDnsHandle] Network $network lost" }
                     handleChange(null)
@@ -83,7 +83,7 @@ class NoConnectionDnsHandle(
                     handleNetworkInfo(activeNetwork)
                 }
             }
-            connectivityManager.registerNetworkCallback(request, networkCallback)
+            networkCallback?.also {  connectivityManager.registerNetworkCallback(request, it) }
         }
         handleNetworkInfo(connectivityManager.activeNetworkInfo)
         if(regularConnectionCheckIntervalMs != null) {
@@ -145,10 +145,8 @@ class NoConnectionDnsHandle(
 
     override fun cleanup() {
         synchronized(this) {
-            if(networkCallback != null) {
-                connectivityManager.unregisterNetworkCallback(networkCallback)
-                networkCallback = null
-            }
+            networkCallback?.also { connectivityManager.unregisterNetworkCallback(it)  }
+            networkCallback = null
             regularConnectionCheckJob?.cancel()
             regularConnectionCheckJob = null
         }