运行本书例12.4和例12.5时，都有同样的错误提示信息，如何解决：

Catchable fatal error:  Argument 1 passed to JpGraphException::defaultHandler() must be an instance of Throwable, instance of JpGraphExceptionL given in C:\AppServ\www\jpgraph\src\jpgraph_errhandler.inc.php on line 158

例12.5代码如下：

<?php

include ("jpgraph/src/jpgraph.php");

include ("jpgraph/src/jpgraph_line.php");

$datay = array(8320,9360,14956,17028,13060,15376,25428,16216,28548,18632,22724,28460);

$graph = new Graph(600,300,"auto");

$graph->img->SetMargin(50,40,30,40);   

$graph->img->SetAntiAliasing();

$graph->SetScale("textlin");

$graph->SetShadow();

$graph->title->Set("2009年《PHP从入门到精通》图书月销售额折线图");

$graph->title->SetFont(FF_SIMSUN,FS_BOLD);

$graph->SetMarginColor("lightblue");

$graph->yaxis->title->SetFont(FF_SIMSUN,FS_BOLD);

$graph->xaxis->SetPos("min");

$graph->yaxis->HideZeroLabel();

$graph->ygrid->SetFill(true,'#EFEFEF@0.5','#BBCCFF@0.5');

$a=array("1月","2月","3月","4月","5月","6月","7月","8月","9月","10月","11月","12月");

$graph->xaxis->SetTickLabels($a);

$graph->xaxis->SetFont(FF_SIMSUN);

$graph->yscale->SetGrace(20); 

$p1 = new LinePlot($datay);

$p1->mark->SetType(MARK_FILLEDCIRCLE);

$p1->mark->SetFillColor("red");

$p1->mark->SetWidth(4);

$p1->SetColor("blue");

$p1->SetCenter();

$graph->Add($p1);

$graph->Stroke();

?>