Bug 131243 Open invalid report design.
Open a invalid report design should switch to XML Source editor page and can't switch to other pages, when the source is correct user can switch to layout and other pages.
UI/org.eclipse.birt.report.designer.ui.editors/src/org/eclipse/birt/report/designer/ui/editors/MultiPageReportEditor.java
/**
	 * Get the current report ModuleHandle.
	 * 
	 * @return
	 */
	public ModuleHandle getModel( )
	{
		if ( model == null )
		{
			IReportProvider provider = EditorUtil.getReportProvider( this,
					getEditorInput( ) );
			if ( provider != null )
			{
				model = provider.getReportModuleHandle( getEditorInput( ) );
				return model;
			}
		}
		return model;
	}
	/*
	 * (non-Javadoc)
	 * 
	 * @see org.eclipse.ui.IPartListener#partActivated(org.eclipse.ui.IWorkbenchPart)
	 */
	public void partActivated( IWorkbenchPart part )
	{
		if ( part != this )
		{
			if ( part instanceof PageBookView )
			{