made the preference store GetCategory method sync (#10847)

* made the preference store GetCategory method sync

* fixed the review comments

store/sqlstore/preference_store.go

@@ -180,23 +180,22 @@ func (s SqlPreferenceStore) Get(userId string, category string, name string) (*m
 	return preference, nil
 }
 
-func (s SqlPreferenceStore) GetCategory(userId string, category string) store.StoreChannel {
-	return store.Do(func(result *store.StoreResult) {
-		var preferences model.Preferences
+func (s SqlPreferenceStore) GetCategory(userId string, category string) (model.Preferences, *model.AppError) {
+	var preferences model.Preferences
 
-		if _, err := s.GetReplica().Select(&preferences,
-			`SELECT
+	if _, err := s.GetReplica().Select(&preferences,
+		`SELECT
 				*
 			FROM
 				Preferences
 			WHERE
 				UserId = :UserId
 				AND Category = :Category`, map[string]interface{}{"UserId": userId, "Category": category}); err != nil {
-			result.Err = model.NewAppError("SqlPreferenceStore.GetCategory", "store.sql_preference.get_category.app_error", nil, err.Error(), http.StatusInternalServerError)
-		} else {
-			result.Data = preferences
-		}
-	})
+		return nil, model.NewAppError("SqlPreferenceStore.GetCategory", "store.sql_preference.get_category.app_error", nil, err.Error(), http.StatusInternalServerError)
+	}
+
+	return preferences, nil
+
 }
 
 func (s SqlPreferenceStore) GetAll(userId string) store.StoreChannel {