I have a folder (actually many of them) containing original files and virtual copies of each file. I used to be able to enable library filters, then choose 'filter by kind', then selct either virtual copies or originals. Now (after upgrading from LR 5.3 to LR 5.4), when I enable library filters, all of my files disappear from the folder. All of the options under 'filter by kind' are grayed out. I tried resetting the filter to no avail. Command+Z brings my files back, but I cannot use the library filters at all. ????