Filter out the special empty string group ("": "用户分组") from the
usable groups in PricingGroups component. This empty group represents
"user's current group" but contains no data and should not be displayed
in the group filter options.
- Add filter condition to exclude empty string keys from usableGroup
- Prevents displaying invalid empty group option in UI
- Improves user experience by showing only valid selectable groups
8a54512037