[Cashtab] Patch API error handling

Summary:
T2491

Add missing console.log statement to API call function
Add type check to result of function to catch network errors

Test Plan:
npm start
confirm this error is not thrown with normal API

Reviewers: #bitcoin_abc, emack

Reviewed By: #bitcoin_abc, emack

Differential Revision: https://reviews.bitcoinabc.org/D11593