IsValid, IsClosed, Handle

I have a question about the suggested method to use in this case.

I had the following code to capture the current pane rectangle:

 CXTPDockingPane * pPane = m_paneManager.FindPane(IDR_MY_PANE);
 if( pPane != NULL && pPane->IsValid() )
 {
    CRect rectPane( pPane->GetPaneWindowRect() );

    // do something with rectPane
}

Now a problem came when the user clicked on the "x" to close the pane and then it came to this code - it throws an exception on the GetPaneWindowRect.   Which led me to wonder why it was not NULL and still valid even after being closed - is that intentional?

Second question, I thought it would be easy to fix by adding a pPane->GetSafeHwnd(); to the if-test but then the build failrue indicates that GetSafeHwnd is a protected member and cannot be called here.  So I looked thru the header file and found the  IsClosed() method and add a !pPane->IsClosed() to the test and that resolves the issue.   Is that the preferred method for handling this situation?

Thanks