Remove stack from exception message

src/rpc/xmlrpc_tinyxml2.cc

@@ -84,19 +84,16 @@ private:
 const tinyxml2::XMLElement*
 element_access(const tinyxml2::XMLElement* elem, std::string element_names) {
   // Helper function to check each step of a element access, in lieu of XPath
-  std::string stack;
   const tinyxml2::XMLElement* result = elem;
   size_t pos = 0;
   do {
     auto previous_pos = pos;
     pos = element_names.find(',', pos + 1);
     auto item = element_names.substr(pos, previous_pos - pos);
-    stack.append(item);
     result = result->FirstChildElement(item.c_str());
     if (result == nullptr) {
-      throw xmlrpc_error(XMLRPC_PARSE_ERROR, "could not find expected element " + stack);
+      throw xmlrpc_error(XMLRPC_PARSE_ERROR, "could not find expected element " + item);
     }
-    stack.append("->");
   } while (pos != std::string::npos);
   return result;
 }