Improve the message that is displayed when error occurs related to node issue

[cointastical]

There were a couple error messages shown to the user trying to either deposit or withdraw.

In one instance, the message consisted of the json for an internal data structure. Specifically, when trying to fund a wallet, after clicking "generate invoice" button, the message shown was:
Error: Unexpected error value: [503, "AddInvoiceError", { err: [Error] }]

In another instance, the message was misleading. Specifically, trying to withdraw by paying an invoice, the message shown was:
Error: could not decode invoice
But the invoice was encoded properly and the invoice could be paid using one of my own LN wallets.

This same message even occurred when trying to withdraw using a Lightning Address, rather than paying an LN Invoice.

Ultimately, these issues were related to a node issue. See SN Item #48781.

So this Github Issue is my request for improvement with the message displayed to the user in the instance where there is a node issue, so that the user only sees when it is necessary for that user to see.