map::iterator is a dependent typename and needs the typename keyword. (…

…#4545)

nano/node/fair_queue.hpp

@@ -340,7 +340,7 @@ class fair_queue final
 
 private:
 	std::map<origin_entry, entry> queues;
-	std::map<origin_entry, entry>::iterator iterator{ queues.end () };
+	typename std::map<origin_entry, entry>::iterator iterator{ queues.end () };
 	size_t counter{ 0 };
 
 	std::chrono::steady_clock::time_point last_update{};