BUGFIX: out of index error in omci-sim

Change-Id: Id10076ff14629f279c2caa0fdfcf197e9cb0188b
diff --git a/omci_sim.go b/omci_sim.go
index a428cb7..20fe8be 100644
--- a/omci_sim.go
+++ b/omci_sim.go
@@ -41,8 +41,10 @@
 
 	resp, err = Handlers[msgType](class, content, key)
 	if err != nil {
-		return resp, err
+		log.Println("%s", err)
+		return resp, nil
 	}
+
 	resp[0] = byte(transactionId >> 8)
 	resp[1] = byte(transactionId & 0xFF)
 	resp[2] = 0x2<<4 | byte(msgType)