**List of steps to reproduce** (step by step, including full links if applicable):
* Go to Special:MassMessage
* Enter a page title
* Press "Preview"
**What happens?**:
An error message saying that "No subject has been provided for the message." and the section dropdown remains empty
**What should have happened instead?**:
The section dropdown should be filled so that the section name can be used as the edit summary / subject.
**Software version (if not a Wikimedia wiki), browser information, screenshots, other information, etc.**:
Up to date Firefox.
**Extra info**
This means that the user has to put something in the summary, which according to the description for that field "is ignored if a section of the page is selected to be sent as subject". Therefore if the user knows they want to use the section title as the subject, this means this field has to be filled in for no good reason.