fixed empty css class attribute for CGridColumn
fixed empty css class attribute for CGridColumn

fixes #1163

guber007/yii,sachintaware/yii,l3xthanzero/trackstar,auburus/yii,kurorido1990/dev-github,trewor-kapusta/yii,longhua828/yii,janisto/yii,mudrezzz/testphp,yiichina/yii,janisto/yii,licailing/yii,dbalencar/yii,phoenix3008/yii,tvs-prarthana/yii,GerrGIT/yii,yiichina/yii,licailing/yii,janisto/yii,makasim/PayumYiiExtensionSandbox,mudrezzz/testphp,ImAnilChaudhari/yii,mqiu/yiis,mudrezzz/testphp,lsjing/yii,longhua828/yii,licailing/yii,YaDelivery/yii,yiichina/yii,yiisoft/yii,trewor-kapusta/yii,kurorido1990/dev-github,ImAnilChaudhari/yii,phoenix3008/yii,tvs-prarthana/yii,phoenix3008/yii,makasim/PayumYiiExtensionSandbox,Infowatch/yii,lubosdz/yii,intersvyaz/yii,Vartacom/yii,scriptius/blog,sachintaware/yii,janisto/yii,Vartacom/yii,scriptius/blog,mqiu/yiis,jackey/YiiAPI-Framework,Yanan1021/yii,Vartacom/yii,longhua828/yii,phoenix3008/yii,intersvyaz/yii,guber007/yii,sachintaware/yii,softark/yii,auburus/yii,ImAnilChaudhari/yii,licailing/yii,YaDelivery/yii,auburus/yii,guber007/yii,lubosdz/yii,YaDelivery/yii,Infowatch/yii,kurorido1990/dev-github,er361/yii-zadanie-somnium,marcovtwout/yii,Corfiot/yii,Yanan1021/yii,Corfiot/yii,tvs-prarthana/yii,ImAnilChaudhari/yii,lubosdz/yii,auburus/yii,Yanan1021/yii,bethrezen/yii,bethrezen/yii,softark/yii,lsjing/yii,makasim/PayumYiiExtensionSandbox,mqiu/yiis,wbfree/yii-tutorial,guber007/yii,Vartacom/yii,GerrGIT/yii,er361/yii-zadanie-somnium,mudrezzz/testphp,marcovtwout/yii,dbalencar/yii,YaDelivery/yii,intersvyaz/yii,er361/yii-zadanie-somnium,lsjing/yii,lsjing/yii,bethrezen/yii,wbfree/yii-tutorial,sachintaware/yii,scriptius/blog,makasim/PayumYiiExtensionSandbox,longhua828/yii,lubosdz/yii,GerrGIT/yii,yiisoft/yii,kurorido1990/dev-github,er361/yii-zadanie-somnium,GerrGIT/yii,marcovtwout/yii,jackey/YiiAPI-Framework,dbalencar/yii,marcovtwout/yii,l3xthanzero/trackstar,scriptius/blog,tvs-prarthana/yii,l3xthanzero/trackstar