Chances are you might have unknowingly inserted a “new movie.” I actually already explained this pertaining to another question so I’ll just cut and paste some of it and revamp it a little here.   Above the timeline on the left side you will see a little “movie reel” button that is to the right of the four timeline icon toggle buttons. It has a drop down arrow on it. You will see that clicking this button shows you how many “movie-timelines” you have on the go within that given file. And I say “movie-timeline” because there might not be a clip in the timeline but it will still register as a movie. You will also see that the little “movie reel” button allows you to re-name each movie but it also allows you to add a new movie. Perhaps you accidently did the latter with the keyboard command Ctrl+Alt+N.
If you see that there are two, then click each one to find out which one is empty; and then I recommend re-naming the one you want to keep; then click back to the empty one.
Now, to completely remove the extra “movie-timeline” that is empty you need to use the “File” menu at the top and scroll down to “Manage Movies.” There you will see, among other things, that you can remove the empty “movie-timeline” from your project. Using these options is how you add multiple movies to burn on one DVD. This is likely what is happening in your case. When you “Add a new movie” via “Manage movies” it doesn’t create a whole new file it simply adds a new timeline ready for a new clip to be inserted. Try not to confuse the two scenarios.   It’s kind of hard to explain and that’s why I differentiate between “movie-timeline” and “movie.” The program just calls it a “movie” but for one to not differentiate between the two would be worse than trying to land an airplane over the phone. I hope this has clarified your invisible movie problem.