Bug 191168 [Regression]Exception occurs when resize masterpage in library
Description: Exception occurs when resize masterpage in library. Build number:2.2.0.v20070606-0630 Regression bug:187443 Steps to reproduce: 1. New a library. 2. Go to Master Page, resize the master page using the ruler. Expected result: 1. Layout works correctly. 2. No exception is thrown out. Error log: An unexpected internal exception occurred.Please see log for detail. Plug-in Provider:Eclipse.org Plug-in Name:BIRT Designer UI Plug-in ID:org.eclipse.birt.report.designer.ui Version:2.2.0.v20070606-0630 Error Code:Error.GUIException.invokedByUnexpectedException Error Message:org.eclipse.birt.report.designer.internal.lib.lalyout.LibraryReportDesignLayout
model/org.eclipse.birt.report.model/src/org/eclipse/birt/report/model/core/Module.java
* throw runtime exception.
	 */
	public void setReadOnly( )
	{
		activityStack = new ReadOnlyActivityStack( );
	}
	/**
	 * Returns the module namespace. Only included library has a non-empty
	 * namespace.
	 * 
	 * @return the module namespace
	 */
	public String getNamespace( )
	{
		return null;
	}
	/**
	 * Loads css with the given css file name. This file name can be absolute or
	 * relative. If the css doesn't exist or fatal error occurs when opening
	 * css,.
	 * 
	 * @param fileName
	 *            css file name
	 * @return the loaded css
	 * @throws StyleSheetException
	 */
	public CssStyleSheet loadCss( String fileName ) throws StyleSheetException
	{
		try
		{