[AlPe]

The signature of my empty.idx is:

$ ll empty.idx 
-rw------- 1 xxx xxx 6144 Dec  8 19:23 empty.idx

$ md5sum empty.idx 
51ebcf397d50e4a2a673f85402ae2a94  empty.idx

$ sha1sum empty.idx 
0ae8d4467819786afe4324355fee50cd8e416f7d  empty.idx

$ hexdump -Cv empty.idx  | head
00000000  53 51 4c 69 74 65 20 66  6f 72 6d 61 74 20 33 00  |SQLite format 3.|
00000010  04 00 01 01 00 40 20 20  00 00 00 23 00 00 00 06  |.....@  ...#....|
00000020  00 00 00 00 00 00 00 00  00 00 00 06 00 00 00 01  |................|
00000030  00 00 00 00 00 00 00 00  00 00 00 01 00 00 00 00  |................|
00000040  00 00 00 00 00 00 00 00  00 00 00 00 00 00 00 00  |................|
00000050  00 00 00 00 00 00 00 00  00 00 00 00 00 00 00 23  |...............#|
00000060  00 2d e2 21 0d 00 00 00  05 01 77 00 03 98 02 cf  |.-.!......w.....|
00000070  02 30 01 dd 01 77 00 00  00 00 00 00 00 00 00 00  |.0...w..........|
00000080  00 00 00 00 00 00 00 00  00 00 00 00 00 00 00 00  |................|
00000090  00 00 00 00 00 00 00 00  00 00 00 00 00 00 00 00  |................|