Add warning to make non-registered channelOpenCb visible

Author: yosuke-wolfssl

src/internal.c

@@ -8960,6 +8960,9 @@ static int DoChannelOpen(WOLFSSH* ssh,
             if (ssh->ctx->channelOpenCb) {
                 ret = ssh->ctx->channelOpenCb(newChannel, ssh->channelOpenCtx);
             }
+            else {
+                WLOG(WS_LOG_WARN, "No channel open callback set, accepting channel open by default");
+            }
             if (ssh->channelListSz == 0)
                 ssh->defaultPeerChannelId = peerChannelId;
         #ifdef WOLFSSH_FWD