correctly pass error to unbind on connection handler

lib/eventmachine.rb

@@ -1414,7 +1414,7 @@ def self.event_callback conn_binding, opcode, data
     if opcode == ConnectionUnbound
       if c = @conns.delete( conn_binding )
         begin
-          if c.original_method(:unbind).arity == 1
+          if c.original_method(:unbind).arity != 0
             c.unbind(data == 0 ? nil : EventMachine::ERRNOS[data])
           else
             c.unbind

tests/test_unbind_reason.rb

@@ -2,6 +2,15 @@
 require 'socket'
 
 class TestUnbindReason < Test::Unit::TestCase
+
+  class StubConnection < EM::Connection
+    attr_reader :error
+    def unbind(reason = nil)
+      @error = reason
+      EM.stop
+    end
+  end
+
   def test_connect_timeout
     error = nil
     EM.run {
@@ -13,7 +22,7 @@ def test_connect_timeout
       }
       conn.pending_connect_timeout = 0.1
     }
-    assert_equal error, Errno::ETIMEDOUT
+    assert_equal Errno::ETIMEDOUT, error
   end
 
   def test_connect_refused
@@ -26,6 +35,14 @@ def test_connect_refused
         end
       }
     }
-    assert_equal error, Errno::ECONNREFUSED
+    assert_equal Errno::ECONNREFUSED, error
+  end
+
+  def test_optional_argument
+    conn = nil
+    EM.run {
+      conn = EM.connect '127.0.0.1', 12388, StubConnection
+    }
+    assert_equal Errno::ECONNREFUSED, conn.error
   end
 end