Figured out the crash, but want to see what valgrind would say.

scene.hpp

@@ -58,5 +58,6 @@ namespace scene {
     void zoom(float mid_x, float mid_y, const std::string& style, float scale);
     void reset(sf::RenderTexture& view);
     void set_end_cb(std::function<void()> cb);
+    void tick();
   };
 }