Resolve "400 error for empty reject text"

What does this mr do?

Fix wrong redirect after checking for empty reject message. Also adds an alert on the page for the user to see what they need to change.

Actions taken to fix bug

Fix redirect url

Does this MR meet the acceptance criteria?

• I have added a changelog entry to reflect the significant changes I made and the bug I fixed.
• A test was created to test the bug.
• I have updated the documentation accordingly.
• I adhere to the style guide.

Closes #305 (closed)