garage_model: fix warning about dead code

src/model/garage.rs

@@ -329,7 +329,7 @@ impl Garage {
 
 	pub async fn locked_helper(&self) -> helper::locked::LockedHelper {
 		let lock = self.bucket_lock.lock().await;
-		helper::locked::LockedHelper(self, lock)
+		helper::locked::LockedHelper(self, Some(lock))
 	}
 }
 

src/model/helper/locked.rs

@@ -27,9 +27,16 @@ use crate::permission::BucketKeyPerm;
 /// See issues: #649, #723
 pub struct LockedHelper<'a>(
 	pub(crate) &'a Garage,
-	pub(crate) tokio::sync::MutexGuard<'a, ()>,
+	pub(crate) Option<tokio::sync::MutexGuard<'a, ()>>,
 );
 
+impl<'a> Drop for LockedHelper<'a> {
+	fn drop(&mut self) {
+		// make it explicit that the mutexguard lives until here
+		drop(self.1.take())
+	}
+}
+
 #[allow(clippy::ptr_arg)]
 impl<'a> LockedHelper<'a> {
 	pub fn bucket(&self) -> BucketHelper<'a> {