Deny Reimbursement Request Not Toasting Error

Description

In #1941 we added the ability to slack the finance channel when a reimbursement request is denied. However, when there is an error with sending the slack message, the error isn't getting correctly displayed in a toast on the frontend. This ticket is to make sure errors from this endpoint get correctly displayed in a toast on the frontend.

Acceptance Criteria

• When there is an error with the deny reimbursement request modal being submitted, it shows up in a red toast on the frontend

Proposed Solution

This may be an issue with all the NERFormModals, so you might need to change that code to fix this. You can access the deny reimbursement request modal by logging in as Vic Stone (a member of the finance team aka Justice League on our local) and clicking the deny option in the dropdown on a reimbursement request

Mocks

No response

Start by logging in as Vic Stone locally and opening the deny option on a reimbursement request. Inspect the NERFormModals error-handling path and reproduce an error while submitting the deny reimbursement request. Done means the endpoint error appears in a red frontend toast, including for the deny reimbursement modal.