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

src/commonTest/kotlin/TransportTest.kt

@@ -6,7 +6,6 @@ import kotlinx.coroutines.channels.SendChannel
 import kotlinx.coroutines.test.runTest
 import net.sergeych.crypto.Key
 import net.sergeych.crypto.initCrypto
-import net.sergeych.kiloparsec.command
 import net.sergeych.kiloparsec.*
 import net.sergeych.mp_logger.Log
 import kotlin.test.*
@@ -17,7 +16,7 @@ fun createTestDevice(): Pair<Transport.Device, Transport.Device> {
     val p2 = Channel<UByteArray>(256)
     val id = ++dcnt
     val d1 = object : Transport.Device {
-        override val input: ReceiveChannel<UByteArray?> = p1
+        override val input: ReceiveChannel<UByteArray> = p1
         override val output: SendChannel<UByteArray> = p2
         override suspend fun close() {
             p2.close()
@@ -28,7 +27,7 @@ fun createTestDevice(): Pair<Transport.Device, Transport.Device> {
         }
     }
     val d2 = object : Transport.Device {
-        override val input: ReceiveChannel<UByteArray?> = p2
+        override val input: ReceiveChannel<UByteArray> = p2
         override val output: SendChannel<UByteArray> = p1
         override suspend fun close() {
             p1.close()