Adding a window to the window manager causes a run-time error if Flash Text Engine is used for MX components

What steps will reproduce the problem?
1. In the projects properties, tick the Flex Compiler option 'Use Flash
Text Engine in MX components' 
2. Create an MDIWindow (window = new MDIWindow())
3. Add the newly created MDIWindow to the windowmanager
(windowManager.add(window)

What is the expected output? 

I expected the window to be displayed, without an error.

What do you see instead?
The expected window plus an error box.

What version of the product are you using? On what operating system?
flexlib - 2.5 -flex4
Mac OsX 10.5

Please provide any additional information below.
In MDIWindowControlsContainer.as, line 123 seems to be the cause of the
problem:

var tf:UITextField = window.getTitleTextField();

Variable tf is declared as UITextField, however, if you set the mentioned
compiler option, the window textfield is of type UIFTETextField, thereby
resulting in tf = null.

In line 126, variable tf is referenced, causing a run time error.

Original issue reported on code.google.com by eugenet...@gmail.com on 2 Apr 2010 at 10:51

wiln / flexlib

Adding a window to the window manager causes a run-time error if Flash Text Engine is used for MX components #291