Show error when unable to get documents to view

[gsproston-scottlogic]

Bug report

Description

We should show an error on the view documents modal if we fail to get any documents.

Reproduction steps

Steps to reproduce the behaviour:

1. Don't run the backend
2. Click on the 'view documents' button in the left panel
3. No error message

Expected behaviour

A clear error message that documents can't be retrieved.

Screenshots

Currently:

Suggested solution:

Software (please complete the following information):

• Browser: Edge

Acceptance criteria

GIVEN the backend isn't running
WHEN the user opens the view documents modal
THEN an error is shown on the modal

[gsproston-scottlogic]

Need some rough idea of what this will look like.

[gsproston-scottlogic]

Updated with a screenshot of what this might look like.