Detect and warn on errors caused by Brave shields

[danimoh]

For example using https://nimiqgiftcards.com/ with enabled brave shields (more specifically the "Cross-site cookies blocked" setting) causes an "Invalid request" error in the Hub on redirect.
This problem seems to occur only for cross-origin requests.
The actual cause has not been investigated yet, but likely access to the session storage or another storage is blocked.
If the problem is within the scope of the rpc lib, the detection should happen there, but appropriate error handling would need to be implemented in the hub.