Failed to add dependencies by using flow-c1 from Testnet sources when un-staged contracts exist in the address.

[btspoony]

Problem

Failed to add dependencies by using flow-c1 from Testnet sources when un-staged contracts exist in the address.

Steps to Reproduce

flow-c1 deps add testnet://{AnyAddressWithUnStagedContracts}.{ValidC1.0ContractName}

Acceptance Criteria

not to panic and throw error.

Context

It should be this line that is causing the error, because C1.0 can not read previous Cadence code.
https://github.com/onflow/flow-cli/blob/master/internal/dependencymanager/dependencyinstaller.go#L322-L325