Bug 123726 "Top n", "Bottom n" in highlight dialog doesn't work.
Description: "Top n", "Bottom n" in highlight dialog doesn't work. Steps to reproduce: 1. Add a highlight for a table. 2. Set highlight rule: "account_id", "top n", "3", let its font color red. 3. Preview the report, it doesn't work. Attached is design file.
data/org.eclipse.birt.data/src/org/eclipse/birt/data/engine/impl/PreparedQuery.java
while ( it.hasNext() )
	    {
	        prepareExpression((IBaseExpression) it.next(), groupLevel, cx, reg);
	    }
	}
	
	/**
	 * Prepares one expression
	 * 
	 * @param expr
	 * @param groupLevel
	 * @param cx
	 * @param reg
	 */
	private void prepareExpression( IBaseExpression expr, int groupLevel,
			Context cx, AggregateRegistry reg )
	{
	    ExpressionCompiler compiler = this.engine.getExpressionCompiler();
	    
	    if ( expr instanceof IScriptExpression )
	    {
	    	String exprText = ((IScriptExpression) expr).getText();
	    	CompiledExpression handle = compiler.compile( exprText, reg, cx);
	    	expr.setHandle( handle );
	    	expr.setID( IDUtil.nextExprID( ) );
	    }
	    else if ( expr instanceof IConditionalExpression )
	    {