Fix coverage.

Author: samuel-williams-shopify

lib/async/scheduler.rb

@@ -61,6 +61,12 @@ def blocking_operation_wait(work)
 
 		private_constant :BlockingOperationWait
 
+		if ::IO::Event.const_defined?(:WorkerPool)
+			WorkerPool = ::IO::Event::WorkerPool
+		else
+			WorkerPool = nil
+		end
+
 		# Create a new scheduler.
 		#
 		# @public Since *Async v1*.
@@ -82,11 +88,7 @@ def initialize(parent = nil, selector: nil, profiler: Profiler&.default, worker_
 			@timers = ::IO::Event::Timers.new
 
 			if worker_pool == true
-				if ::IO::Event.const_defined?(:WorkerPool)
-					@worker_pool = ::IO::Event::WorkerPool.new
-				else
-					@worker_pool = nil
-				end
+				@worker_pool = WorkerPool&.new
 			else
 				@worker_pool = worker_pool
 			end