Fix: remove unnecessary unsafe of ErasedBundleTemplate::apply

[yilin0518]

Objective

ErasedBundleTemplate::apply in bevy_scene was declared unsafe fn, but its # Safety contract was stale and unenforceable. The documented precondition referenced a bundle_writer parameter that this method does not have — the wording seems copied from ErasedComponentTemplate::apply, which does take a bundle_writer: &mut BundleWriter and uses it inside an unsafe call. On ErasedBundleTemplate::apply there is no bundle_writer, so the stated caller-side obligation cannot be satisfied or verified.

The default blanket impl only performs safe operations:

impl<T: Template<Output: Bundle> + Send + Sync + 'static> ErasedBundleTemplate for T {
    unsafe fn apply(&self, context: &mut TemplateContext) -> Result<(), BevyError> {
        let bundle = self.build_template(context)?;
        context.entity.insert(bundle);
        Ok(())
    }
}

build_template and EntityWorldMut::insert are both safe, so the unsafe marker imposed a caller obligation the body never needed.

Solution

Drop the unnecessary unsafe and remove the stale # Safety documentation, since no real caller-verifiable invariant exists for this method:

Testing

The computer I use don't install the msvc, so I use the following command to test

• cargo +nightly-x86_64-pc-windows-gnu build -p bevy_scene: Successfully build
• cargo +nightly-x86_64-pc-windows-gnu test -p bevy_scene: Pass

---