fix the npe in the hashCode method when subscriptionDataSet is null

Author: 1782935682

remoting/src/main/java/org/apache/rocketmq/remoting/protocol/subscription/SubscriptionGroupConfig.java

@@ -19,6 +19,7 @@
 
 import com.google.common.base.MoreObjects;
 import java.util.HashMap;
+import java.util.HashSet;
 import java.util.Map;
 import java.util.Set;
 import org.apache.commons.lang3.builder.EqualsBuilder;
@@ -49,7 +50,7 @@ public class SubscriptionGroupConfig {
     // Only valid for push consumer
     private int consumeTimeoutMinute = 15;
 
-    private Set<SimpleSubscriptionData> subscriptionDataSet;
+    private Set<SimpleSubscriptionData> subscriptionDataSet = new HashSet<>();
 
     private Map<String, String> attributes = new HashMap<>();