FIO-7637: add catch block to subform submission loading

[brendanbond]

Link to Jira Ticket

https://formio.atlassian.net/browse/FIO-7637

Description

A customer had an urgent production issue - their servers were crashing with unhandled promise exceptions. Upon investigation, the server-side formio.js renderer is attempting to load subform submissions from a baseUrl that is not set, ending in a "Invalid Alias" error. Since Formio.request rejects on 4xx responses, the server will crash because NodeJS expects you to handle uncaught Promise exceptions.

An alternative might have been to examine why Formio.request rejects on 4xx responses rather than delegating handling non network errors to the caller (a lá the fetch web api), but due to the urgency of this ticket for the customer in question and the potential disruption of a change to Formio.request, this seems like the most suitable solution for the moment.

Dependencies

n/a

How has this PR been tested?

n/a

Checklist:

• I have commented my code, particularly in hard-to-understand areas
• I have made corresponding changes to the documentation (if applicable)
• My changes generate no new warnings
• My changes include tests that prove my fix is effective (or that my feature works as intended)
• New and existing unit/integration tests pass locally with my changes
• Any dependent changes have corresponding PRs that are listed above

[travist]

👍