removed nullable array from transport device, as channels close() is more than enough

src/jvmMain/kotlin/net/sergeych/kiloparsec/adapter/asyncSocketToDevice.kt

@@ -98,7 +98,7 @@ suspend fun asyncSocketToDevice(socket: AsynchronousSocketChannel): InetTranspor
                 }
             }
             // transport device copes with blocks:
-            val inputBlocks = Channel<UByteArray?>()
+            val inputBlocks = Channel<UByteArray>()
             // decode blocks from a byte channel read from the socket:
             launch {
                 try {
@@ -116,9 +116,7 @@ suspend fun asyncSocketToDevice(socket: AsynchronousSocketChannel): InetTranspor
                         }
                     }
                 } catch (_: CancellationException) {
-                    inputBlocks.send(null)
                 } catch (_: ClosedReceiveChannelException) {
-                    inputBlocks.send(null)
                     stop()
                 }
                 receiving.value = false