修复 font 不合法 导致出错 
修复 font 不合法 导致出错 

类似于 http://bugs.jquery.com/ticket/5509 这个bug
和 processFontStyle 函数中 506 行的try 左右相同
powy1993/zrender,laomu1988/zrender,elancom/zrender,KnightBubble/zrender,ekinwei/zrender,IveWong/zrender,noikiy/zrender,dato-code/zrender,IveWong/zrender,dato-code/zrender,lkiarest/zrender,nagyistoce/ecomfe-zrender,powy1993/zrender,songshuang00/zrender,ChaosPower/zrender,skyujilong/zrender,ecomfe/zrender,laomu1988/zrender,noikiy/zrender,coderstudy/zrender,uooo/zrender,stanleyxu2005/zrender,KnightBubble/zrender,powy1993/zrender,dasmond/zrender,dasmond/zrender,ilovezy/zrender,ChaosPower/zrender,jl9n/zrender,ecomfe/zrender,ecomfe/zrender,armslave00/zrender,lkiarest/zrender,uooo/zrender,nagyistoce/ecomfe-zrender,songshuang00/zrender,coderstudy/zrender,ilovezy/zrender,armslave00/zrender,jl9n/zrender,skyujilong/zrender,stanleyxu2005/zrender,ekinwei/zrender,elancom/zrender