I used the multi-diff feature and used the "<< Merge All" button. When I went to close the diff it normally asks if you would like to save the changes of the file. This time it had no filename (see attached photo). If I select "Yes", it says "Missing filename" (see attached photo). I do a bunch of diffs a day and this is the first time I've seen it.
I am running Ubuntu 16.04, SE Beta 6.