Update ManagingWindow.md

The message `withWindowDo:` should have a receiver

Author: LNUitTutor

Chapters/ManagingWindow/ManagingWindow.md

@@ -157,7 +157,7 @@ dialog
 The message `withWindowDo:` makes sure that the presenter that scheduled the window still exists or is in a state that makes sense.
 
 ```
-withWindowDo: [ :window | window title: 'MyTitle' ]
+presenter withWindowDo: [ :window | window title: 'MyTitle' ]
 ```
 
 
@@ -449,4 +449,4 @@ WindowExamplePresenter >> initializeDialogWindow: aDialogWindowPresenter
 ### Conclusion
 
 
-In this chapter, we treated the features of Spec that have to do with windows. First we described opening and closing windows as well as how to open a window as a dialog box. That was followed by configuring the window's size and its decorating widgets. After highlighting small yet important details of the window like its title and the about text, the chapter ended with handling dialogs.
+In this chapter, we treated the features of Spec that have to do with windows. First we described opening and closing windows as well as how to open a window as a dialog box. That was followed by configuring the window's size and its decorating widgets. After highlighting small yet important details of the window like its title and the about text, the chapter ended with handling dialogs.