Fix typo 'Maximum number of classes if'

src/extractor/extractor.cpp

@@ -104,7 +104,7 @@ void SetClassNames(const std::vector<std::string> &class_names,
                 auto index = classes_map.size();
                 if (index > MAX_CLASS_INDEX)
                 {
-                    throw util::exception("Maximum number of classes if " +
+                    throw util::exception("Maximum number of classes is " +
                                           std::to_string(MAX_CLASS_INDEX + 1));
                 }
 

src/extractor/extractor_callbacks.cpp

@@ -188,7 +188,7 @@ void ExtractorCallbacks::ProcessWay(const osmium::Way &input_way, const Extracti
         {
             if (classes_map.size() > MAX_CLASS_INDEX)
             {
-                throw util::exception("Maximum number of classes if " +
+                throw util::exception("Maximum number of classes is " +
                                       std::to_string(MAX_CLASS_INDEX + 1));
             }
             ClassData class_mask = getClassData(classes_map.size());