The GUI management is optional - you can still manage this system over CLI via ssh or telnet.
The official fix is to put the ontap.exe file for 7.2.1P4 back on the system and run "software install ontap.exe", then reboot when the OS reinstall is done.
You can probably do it via the command line with:
priv set diag
mv /etc/.onboot/java /etc/java
reboot
Good luck!