It's possible that the monitor was closed before calling resume. This…

… happens if `select` returns several tasks to resume, and a previous one calls close on this wrapper.

lib/async/version.rb

@@ -19,5 +19,5 @@
 # THE SOFTWARE.
 
 module Async
-	VERSION = "1.10.0"
+	VERSION = "1.10.1"
 end

lib/async/wrapper.rb

@@ -50,6 +50,9 @@ def initialize(io, reactor = nil)
 		end
 
 		def resume(*args)
+			# It's possible that the monitor was closed before calling resume.
+			return unless @monitor
+
 			readiness = @monitor.readiness
 
 			if @readable and (readiness == :r or readiness == :rw)

spec/async/wrapper_spec.rb

@@ -81,13 +81,19 @@
 		it "can be cancelled while waiting to be readable" do
 			reactor.async do
 				expect do
-					output.wait_readable
+					input.wait_readable
 				end.to raise_error(Async::Wrapper::Cancelled)
 			end
 
-			reactor.async do
-				input.close
-			end
+			# This reproduces the race condition that can occur if two tasks are resumed in sequence.
+
+			# Resume task 1 which closes IO:
+			output.close
+
+			# Resume task 2:
+			expect do
+				output.resume
+			end.to_not raise_error
 		end
 
 		it "can be cancelled" do