Bug 121687 Exception throws when export data in table which inside a grid cell.
Description: Exception throws when export data in table which inside a grid cell. Steps to reproduce: 1. insert a grid. 2. insert one table to one grid cell. 3. insert another table to the other grid cell. 4. export data in two tables. Expected result: Data are exported. Actual result: Exception in: ReportEngineService.getMetaData( )
engine/org.eclipse.birt.report.engine/src/org/eclipse/birt/report/engine/parser/EngineIRVisitor.java
* unique name to it and then add it to the style list.
	 * 
	 * @param style
	 *            The <code>StyleDeclaration</code> object.
	 * @return the name of the style.
	 */
	private String assignStyleName( StyleDeclaration style )
	{
		if ( style == null || style.isEmpty( ) )
		{
			return null;
		}
		
		for ( int i = 0; i < report.getStyleCount( ); i++ )
		{
			
			StyleDeclaration cachedStyle = (StyleDeclaration) report
					.getStyle( i );
			if ( cachedStyle.equals( style ) )
			{
				
				
				style = cachedStyle;
				return Report.PREFIX_STYLE_NAME + i;
			}
		}
		
		
		
		String styleName = Report.PREFIX_STYLE_NAME + report.getStyleCount( );