gracefully handle errors when fetching lnurlp wellknown info (#960)

if `fetch` or `req.json` fails, catch those errors and return a default error to the user

if the res payload indicates error but doesn't return a `reason`, also return the same
default error message to the user

lib/lnurl.js

@@ -33,10 +33,19 @@ export async function lnAddrOptions (addr) {
     // support HTTP and HTTPS during development
     protocol = process.env.PUBLIC_URL.split('://')[0]
   }
-  const req = await fetch(`${protocol}://${domain}/.well-known/lnurlp/${name}`)
+  const unexpectedErrorMessage = `An unexpected error occurred fetching the Lightning Address metadata for ${addr}. Check the address and try again.`
-  const res = await req.json()
+  let res
+  try {
+    const req = await fetch(`${protocol}://${domain}/.well-known/lnurlp/${name}`)
+    res = await req.json()
+  } catch (err) {
+    // If `fetch` fails, or if `req.json` fails, catch it here and surface a reasonable error
+    console.log('Error fetching lnurlp', err)
+    throw new Error(unexpectedErrorMessage)
+  }
   if (res.status === 'ERROR') {
-    throw new Error(res.reason)
+    // if the response doesn't adhere to spec by providing a `reason` entry, returns a default error message
+    throw new Error(res.reason ?? unexpectedErrorMessage)
   }
 
   const { minSendable, maxSendable, ...leftOver } = res