Did you put transitions on to your clips such as crossfades? If there is a crossfade or dip to black transition on the end of your last clip, your logo, then it will fade to black. You'll need to delete that transition.
Now, in RUSH when previewing your project after your last frame plays the Program Monitor will turn black. After I export out a video and play it in QuickTime the video hold on the last frame at the end. I'm not sure all video players behave this way. So try exporting your project and see what the results are in your video player of choice.
Hello! It's october 2020 and I have the same issue. I'd like to use transitions in my 15 seconds video but at the end I'm adding a logo over the fade to white transition, and by default it fades to black as well at the end. WHY? What if you want the end of the video fade to white? You can't?
The solution I came with is make the video longer, and then export it, open it in Quicktime and cut the final fade to black part. Stupid to do this, but at least you can fix it.