Un-deleteable quest that can't be completed

I have this Quest:
But I have already done this:
How do I get rid of the quest AND keep my Tiger mount?

Complete the quest line again, and don’t ask Tamarin for another tiger (that removes your current tiger pet or mount).
This quest may require you to kill the corrupted who are in north of CHOSAIN. (some quest(s) require you to kill those instead of those in Kara Korum)

There is no option from Tamarin to restart the quest. The only option he gives will delete my mount.

If you do not have any tiger pet, just /petition it.