return false when failed open map

src/game/World.cpp

@@ -59,6 +59,7 @@ bool World::loadMapFromFile(const std::string& fileName) {
     DataBuffer buffer;
     if (!buffer.ReadFile(fileName)) {
         std::cerr << "Failed to load map from file " << fileName << " !\n";
+        return false;
     }
 
     std::cout << "Read file : " << fileName << " (File size : " << buffer.GetSize() << ")" << std::endl;