[24389] Fix initial ID rendering without schema

As the work packages from the list response have no schema, but are
used to build the table, they initially have no schema yet.

frontend/app/components/work-packages/wp-display-attr/wp-display-attr.directive.ts

@@ -53,7 +53,7 @@ export class WorkPackageDisplayAttributeController {
               protected $scope: ng.IScope) {
 
     // Update the attribute initially
-    if (this.workPackage) {
+    if (this.workPackage && this.customSchema && this.schema[this.attribute]) {
       this.updateAttribute(this.workPackage);
     }
   }