We are getting 400 bad requests on TM merge translations for project version which does not contain a document.
Step to reproduce:
Login to zanata.
Go to dashboard
Create new project
Create new version
Do not upload any document
Select that version
Open a browser console by inspect.
Select "^" down arrow after settings options
Click TM Merge translation
Observe the console
400 bad request in console
There should be the proper message if there is no document.
Like message shows on copy translation if there is no document
Attached screen captured for more info.