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
* @param signature
	 *            the UTF signature of the module file.
	 */
	public void setUTFSignature( String signature )
	{
		this.signature = signature;
	}
	/**
	 * Gets the UTF signature of this module file.
	 * 
	 * @return the UTF signature of the module file.
	 */
	public String getUTFSignature( )
	{
		return signature;
	}
	/**
	 * Returns the number of slots of the module. For the library and the report
	 * design, this number is different.
	 * 
	 * @return the number of slots of the module
	 */
	protected abstract int getSlotCount( );
	/*
	 * (non-Javadoc)
	 * 
	 * @see org.eclipse.birt.report.model.core.DesignElement#getSlot(int)
	 */
	public ContainerSlot getSlot( int slot )
	{