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/ir/Report.java
* 
	 * @return style number
	 */
	public int getStyleCount( )
	{
		return this.styles.size( );
	}
	/**
	 * get the style.
	 * 
	 * @param index
	 *            style index
	 * @return style
	 */
	public IStyle getStyle( int index )
	{
		assert ( index >= 0 && index < styles.size( ) );
		return (IStyle) this.styles.get( index );
	}
	/**
	 * add a style definition into the report.
	 * 
	 * @param style
	 *            style definition.
	 */
	public void addStyle( String name, CSSStyleDeclaration style )
	{
		assert ( style != null );
		this.styles.add( style );
		this.styleTable.put( name, style );