Bug 153040 Template definition should be removed after the report item is deleted
Steps to reproduce: 1.New a report, extends lib.label 2.Convert the label to template report item, and revert it back to the report item 3.Delete the label 4.Remove the included library Expected result: Library can be removed Actual result: A BIRT exception occurred. Plug-in Provider:Eclipse.org Plug-in Name:BIRT Model Plug-in ID:org.eclipse.birt.report.model Version:2.1.0.v20060808-0630 Error Code:Error.LibraryException.LIBRARY_HAS_DESCENDENTS Error Message:The library "Lib" can no be dropped because it has descendents "NewLabel" in the current module.
model/org.eclipse.birt.report.model/src/org/eclipse/birt/report/model/metadata/MetaDataDictionary.java
* 
	 * @return the extension definition list. Return empty list if no extension
	 *         is found.
	 */
	public List getExtensions( )
	{
		if ( extensionNameMap == null )
			return Collections.EMPTY_LIST;
		return new ArrayList( extensionNameMap.values( ) );
	}
	/**
	 * Returns the extension definition given the extension name.
	 * 
	 * @param name
	 *            name of the extension to get
	 * @return the extension definition if found
	 */
	public IElementDefn getExtension( String name )
	{
		if ( extensionNameMap == null )
			return null;
		return (IElementDefn) extensionNameMap.get( name );
	}
	/**
	 * Adds the extension definition to the dictionary.
	 * 
	 * @param extDefn
	 *            the definition of the extension element to add
	 * @throws MetaDataException
	 *             if the extension name is not provided or duplicate.