Handle error cases better

[AlexNi245]

The Dm3 client often assumes that requests and their responses are always successful and valid. That however might not always be the case.
If an error occurs, the client should still work and not crash.

Every request executed during "fetching contract" should be handled as it could fail.

[AlexNi245]

@Bhupesh-mfsi please go through the code and compile a list of every interaction that could cause an error