thingsboard-memoizeit

diff --git a/transport/mqtt/src/main/java/org/thingsboard/server/transport/mqtt/session/GatewaySessionCtx.java b/transport/mqtt/src/main/java/org/thingsboard/server/transport/mqtt/session/GatewaySessionCtx.java
index cfba944..69ed17f 100644
--- a/transport/mqtt/src/main/java/org/thingsboard/server/transport/mqtt/session/GatewaySessionCtx.java
+++ b/transport/mqtt/src/main/java/org/thingsboard/server/transport/mqtt/session/GatewaySessionCtx.java
@@ -17,6 +17,7 @@ package org.thingsboard.server.transport.mqtt.session;
 
 import com.google.gson.JsonArray;
 import com.google.gson.JsonElement;
+import com.google.gson.JsonNull;
 import com.google.gson.JsonObject;
 import com.google.gson.JsonSyntaxException;
 import io.netty.channel.ChannelHandlerContext;
@@ -240,7 +241,7 @@ public class GatewaySessionCtx {
 
     private String getDeviceType(JsonElement json) throws AdaptorException {
         JsonElement type = json.getAsJsonObject().get("type");
-        return type == null ? DEFAULT_DEVICE_TYPE : type.getAsString();
+        return type == null || type instanceof JsonNull ? DEFAULT_DEVICE_TYPE : type.getAsString();
     }
 
     private JsonElement getJson(MqttPublishMessage mqttMsg) throws AdaptorException {