HandlerFeedGenerator: Error when cat does not exists (instead of empty feed)

handlers/handlerfeedgenerator.cpp

@@ -21,6 +21,10 @@ std::vector<HandlerFeedGenerator::EntryRevisionPair> HandlerFeedGenerator::fetch
 		auto categoryDao = this->database->createCategoryDao();
 		for(std::string cat : categories)
 		{
+			if(!categoryDao->find(cat))
+			{
+				throw std::runtime_error("No such category");
+			}
 			auto catmembers = categoryDao->fetchMembers(cat, option);
 			std::copy(catmembers.begin(), catmembers.end(), std::inserter(members, members.end()));
 		}