ROENROLL-1758 fix grades switch to correctly handle missing user pref

src/app/degree-planner/degree-planner.component.ts

@@ -85,10 +85,7 @@ export class DegreePlannerComponent implements OnInit {
       filter(isntUndefined),
     );
 
-    this.showGrades$ = this.store.pipe(
-      select(selectors.getUserPreference, 'degreePlannerGradesVisibility'),
-      map(showGrades => showGrades === true),
-    );
+    this.showGrades$ = this.store.pipe(select(selectors.selectGradeVisibility));
 
     this.hasDismissedIEWarning$ = this.store.pipe(
       select(selectors.getUserPreference, 'degreePlannerHasDismissedIEWarning'),