Manage list when safe has no Collectibles

[francovenica]

Right now the "Manage list" of tokens for the collectibles list shows a loading icon if the safe has no collectibles, making the user think that he should wait for something.

I suggest to show an "empty list" type of message there.

URL: https://safe-team.dev.gnosisdev.com/app/#/safes/0x190F2b3d5E9a78eB54D9d1Ec1B16E92cCbC7ae7b/balances/collectibles