Guard against VisibilityClass duplicates

Author: it-me-joda

crates/bevy_camera/src/visibility/mod.rs

@@ -679,8 +679,14 @@ pub fn add_visibility_class<C>(
 ) where
     C: 'static,
 {
-    if let Some(mut visibility_class) = world.get_mut::<VisibilityClass>(entity) {
-        visibility_class.push(TypeId::of::<C>());
+    let Some(mut visibility_class) = world.get_mut::<VisibilityClass>(entity) else {
+        // potentially warn in this case?
+        return;
+    };
+
+    let type_id = TypeId::of::<C>();
+    if !visibility_class.contains(&type_id) {
+        visibility_class.push(type_id);
     }
 }