Thanks, pgriffet, but that's actually a different thing.
I've explored the problem again... and I must say it's very strange and quite random (and it doesn't have anything to do with zero-byte files). In a particular configuration, I have repeatedly done
exactly the same and the "empty folder" sometimes appeared, sometimes not.
It seems to be connected with the fact that the left and right pannel display "similar" paths.
In particular, I did the following:
1. I prepared the following files:
C:\Temp\X\1\File1.exe
C:\Temp\X\1\File1.txt
C:\Temp\X\2\File2.exe
C:\Temp\X\2\File2.txt
There was nothing else in the C:\Temp directory, only these 4 files.
2. I opened the folder C:\Temp in both the panels (left & right).
3. In the left panel, I copied the folder X to (a new) folder Y, i.e. 4 new files were created:
C:\Temp\Y\1\File1.exe
C:\Temp\Y\1\File1.txt
C:\Temp\Y\2\File2.exe
C:\Temp\Y\2\File2.txt
4. In the right panel, I entered the new folder Y and pressed Ctrl+B.
5. I selected the two .txt files and deleted them.
At this moment, the right panel often showed an empty folder (even though on refresh is showed the real content - the two .exe files inside the folders 1 and 2 were still there).
I repeated the steps 2-5 multiple times, each time deleting the folder Y first. It's hard to estimate, but I'd say the probability that an empty folder will appear is about 50%.
However, when I change the "configuration" such that I copy the folder D:\X (and not C:\X, as before) onto C:\Y, the problem doesn't appear... therefore I said it seems to be connected to the fact that "similar" (i.e. having a common first part?) folders are displayed in the left and right panel.
But of course, I may be completely wrong... and overlooking something obvious
