fixed warning in screen.go

screen.go

@@ -1,7 +1,6 @@
 package tui
 
 import (
-	"errors"
 	"fmt"
 
 	"git.tordarus.net/Tordarus/adverr"
@@ -107,7 +106,7 @@ func (s *Screen) eventloop() {
 		case *tcell.EventMouse:
 			s.onMouseClicked(convertMouseEvent(event))
 		default:
-			s.StopWithError(errors.New(fmt.Sprintf("%#v", event)))
+			s.StopWithError(fmt.Errorf("%#v", event))
 		}
 	}
 }