ng-class工作不正常

Question

我正在尝试将CS​​S类有条件地应用于tr，但它会在条件为true的情况下应用该类。这是我的HTML：

<tr ng-repeat="g in assgnedHeads" 
    ng-if="g.billHeadShortForm!='FEC' && g.billHeadShortForm!='FDG' && g.billHeadShortForm!='GL'"
    ng-class="{'mapped-head':g.pkno!=0}">