Hide fixed table header in entity attributes table when in widget selection mode.

ui/src/app/entity/attribute/attribute-table.tpl.html

@@ -126,7 +126,7 @@
         </md-toolbar>
         <md-table-container ng-show="mode!='widget'">
             <table class="tb-attribute-table" md-table md-row-select multiple="" ng-model="selectedAttributes" md-progress="attributesDeferred.promise">
-                <thead fix-head md-head md-order="query.order" md-on-reorder="onReorder">
+                <thead ng-show="mode!='widget'" fix-head md-head md-order="query.order" md-on-reorder="onReorder">
                     <tr md-row>
                         <th md-column md-order-by="lastUpdateTs"><span translate>attribute.last-update-time</span></th>
                         <th md-column md-order-by="key"><span translate>attribute.key</span></th>