Fix race in 'executeOperation(props:operation)' (#9)

If the task got cancelled while still waiting for dependencies, 'completePendingTask(with:)' was not executed, leaving a zombie in the queue.

Author: mchakravarty

Sources/Queue/AsyncQueue.swift

@@ -118,14 +118,14 @@ public final class AsyncQueue: @unchecked Sendable {
 		props: ExecutionProperties,
 		@_inheritActorContext operation: @escaping ThrowingOperation<Success>
 	) async rethrows -> Success {
-		for awaitable in props.dependencies {
-			await awaitable.waitForCompletion()
-		}
-
 		defer {
 			completePendingTask(with: props)
 		}
 
+		for awaitable in props.dependencies {
+			await awaitable.waitForCompletion()
+		}
+
 		do {
 			return try await operation()
 		} catch is CancellationError {