Drop ghost trailing crumb at directory root
FileView's active-crumb slot was unconditionally rendering the current
directory's decrypted name. At the root, that stacked the root dir's
name ("/") on top of the already-present "Your Cabinet" / workspace
root link, so DaisyUI painted an extra separator and the user saw
`Your Cabinet / /`. Only render the active crumb when we're inside a
subdirectory.