Avoid trying to get unlockedGrantAmount on proposed grants

[damianmarti]

We are getting this error from the blockchain:

eth_call
Contract call: Stream#unlockedGrantAmount
From: 0xf39fd6e51aad88f6f4ce6ab8827279cfffb92266
To: 0xdc64a140aa3e981100a9beca4e685f962f0cf6c9

Error: VM Exception while processing transaction: reverted with custom error 'NoActiveStream()

If contractGrantId do no exists, do not call unlockedGrantAmount.