fixes vertice and index creation in geometry shader mode

src/app_data.rs

@@ -53,4 +53,6 @@ pub struct AppData {
     pub color_image_memory: vk::DeviceMemory,
     pub color_image_view: vk::ImageView,
     pub use_geometry_shader: bool,
+
+    pub topology: vk::PrimitiveTopology,
 }