This message is a double panic and was actually caused by an assertion
panic in:
vfs/vfscache/downloaders/downloaders.go
This is triggered by the code added relatively recently to fix a bug
with renaming files:
ec72432cecdc4eee vfs: fix failed to _ensure cache internal error: downloaders is nil error
So it appears that item.o may be nil at this point.
This patch detects item.o being nil and fetches it again with NewObject.
Fixes#6190Fixes#6235