little fix for more error handling

src/serializationmanager.cpp

@@ -399,6 +399,8 @@ Serializable* ObjectLoader::quickLoad(std::string filename, std::string type, bo
     std::fstream file;
     auto mode = binary ? std::ios_base::in | std::ios_base::binary : std::ios_base::in;
     file.open(filename, mode);
+    if(!file.is_open())
+        return nullptr;
     ObjectLoader loader;
     loader.loadAscii(file);
     file.close();