Detect server error in account state

[SebastienGllmt]

Due to instability of the node, sometimes the server is down or the account state endpoint returns the wrong result. To avoid users panicking, I try and detect these errors client-side and report an error in the UI

Notably

1. Show an error message to the user instead of saying their ADA is not delegated
2. Show the "total rewards" and "total delegated" as spinners instead of 0 ADA