If create report fails, show toast with error message

[Nutomic]

Requirements

• This is a bug report, and if not, please post to https://lemmy.ml/c/lemmy_support instead.
• Please check to see if this issue already exists.
• It's a single bug. Do not report multiple bugs in one issue.
• It's a frontend issue, not a backend issue; Otherwise please create an issue on the backend repo instead.

Summary

When creating a new report fails, there is no indication in the UI and only the browser console shows an error message. It should display a toast.

Related to LemmyNet/lemmy#6214.

Steps to Reproduce

1. Create a new post report
2. This should work fine and show a success toast
3. Create a second report for the same post

Technical Details

Creating a duplicate report will fail as expected, however there is no error toast in the UI.

Lemmy Instance Version

1.0.0

Lemmy Instance URL

No response