[xDai] Review RPC interactions and properly handle return values

[fernandomg]

One of the issues that arose during the implementation of xDai:

remoteOwner was null as the RPC call failed to succeed.

We need to be sure that all the interactions with the RPC are properly handled (also, for this particular case https://github.com/gnosis/safe-react/blob/b7afc5caea6e57473152afc8f1bb598358aca4e4/src/logic/contracts/generateBatchRequests.ts#L13 should be properly typed)