Bug 193285 Add CSS file has issue when delete the css file in library explorer.
Description: Add CSS file has issue when delete the css file. Build number:2.2.0.v20070619 Steps to reproduce: 1. In library explorer, add a css file. 2. Use the css file in report. 3. Delete the css file in Library Explorer. 4. In report outline, select the css file, right click and select reload CSS file menu. 5. Delete the css file in outline. Expected result: After step4, Exception throws out. Step 5 can be done. Actual result: After step4, the css file in report outline can not be deleted. Error log:n/a
model/org.eclipse.birt.report.model/src/org/eclipse/birt/report/model/css/CssStyleSheetHandleAdapter.java
{
			return false;
		}
		String fileName = sheetHandle.getFileName();
		return canAddCssStyleSheet( fileName );
	}
	 
	/**
	 * Reloads the css with the given css file path. If the css style sheet
	 * already is included directly or indirectly, reload it. If the css is not
	 * included, exception will be thrown.
	 * 
	 * @param sheetHandle
	 *            css style sheet handle
	 * @throws SemanticException
	 *             if error is encountered when handling
	 *             <code>IncludeCssStyleSheet</code> structure list. Or it
	 *             maybe because that the given css is not found in the design.
	 *             Or that the css has descedents in the current module
	 */
	 public final void reloadCss( CssStyleSheetHandle sheetHandle ) throws SemanticException
	 {
		 if ( sheetHandle == null )
			 return;
	
		 CssCommand command = new CssCommand( module, element );
		 command.reloadCss( sheetHandle.getStyleSheet( ) );
	 }
}