Fix antlr#4656

Remove duplicated element
Signed-off-by: Thomas <thomas.burg@gmail.com>

runtime/Cpp/runtime/src/tree/xpath/XPath.cpp

@@ -147,7 +147,13 @@ std::vector<ParseTree *> XPath::evaluate(ParseTree *t) {
       }
     }
     i++;
-    work = next;
+    // remove duplicated element
+    work.clear();
+    for (unsigned int i=0; i < next.size(); i++ ){
+        if (std::find(work.begin(),work.end(),next[i]) == std::end(work)) {
+          work.push_back(next[i]);
+	}
+    }
   }
 
   return work;