There are frames in every After Effects composition, so that’s not your problem. Your issue is either (A.) there are black frames after you made a cut in the first section (B.) there are black frames at the beginning of your second section or (C.) the software you are using is inserting a space between the two clips.
I would check each clip individually, and if both look clean and you still have issues, I would take Dave’s suggestion and bring them into Premiere (Or even AE again) to combine. Then you can see how it plays back and adjust anything if needed.