Fixed segfault that happend when you'd exit the ingame-state.

src/presentation/states/state_ingame.c

@@ -91,7 +91,10 @@ static void state_render(Presentation_State *state) {
     ClearBackground((Color) { 240, 236, 226, 255 });
 
     Simulation_World *sim_world = &g_current_session->simulation_world;
+    assert(sim_world != NULL);
+
     Game_World *world = sim_world->game_world;
+    assert(world != NULL);
     Grid *grid = &world->grid;
 
     uint32_t grid_total_size = grid->width * grid->height;