Reproduce steps:
1. plug a NIC card to system
2. boot and select "Boot Maintenance Manager"->"Driver Options"->"Add Driver Option", a "MAC" device path will show up
3. select "MAC" device path and press Enter, and then press ESC
4. select "MAC" device path again, then the UI will hang.
git-svn-id: https://edk2.svn.sourceforge.net/svnroot/edk2/trunk/edk2@9367 6f19259b-4bc3-4df7-8a09-765794883524