fix: show "clear delegations" button only when there is existing delegations

[wa0x6e]

Summary

This PR fix an issue where the "clear delegations" button in the split delegation modal was always appearing (it should be hidden when there are no existing delegations)

How to test

1. Go to http://localhost:8081/#/test.wa0x6e.eth/delegates?delegate=
2. The "clear delegation" link should not appear if you don't have any existing delegations
3. Login as 0x674a5A935c8A23EEA552478E5Dfc65f88a357665 using impersonator
4. Go to http://localhost:8081/#/paraswap-dao.eth/delegates?delegate=
5. There should be existing delegations, and the clear delegations button should appear

[ChaituVR]

utAck