Return true for isEmpty() if the pair is equal to the empty pair

app/src/main/java/com/frostnerd/dnschanger/database/entities/IPPortPair.java

@@ -110,7 +110,7 @@ public class IPPortPair extends MultitonEntity implements Serializable{
     }
 
     public boolean isEmpty(){
-        return getAddress().equals("");
+        return getAddress().equals("") || this == getEmptyPair();
     }
 
 }
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