[minor] indexer treats fifo file as directory

[nahoj]

This is an issue that doesn't affect the generated index, that I can see. It just outputs a wrong error log.

This happens with both v2.1.53 and v3.0.2, using node.js v16.20.1.

/mnt/test/loc$ ls -l
total 4,0K
drwxrwxr-x 2 jg jg 4,0K juil.  8 12:22 dir
prw-rw-r-- 1 jg jg    0 juil.  8 12:22 fifo
-rw-rw-r-- 1 jg jg    0 juil.  8 12:03 file
lrwxrwxrwx 1 jg jg    4 juil.  8 12:23 symlink -> file
/mnt/test/loc$ tscmd -m indexer .
Error listing meta directory ./dir/.ts
Error listing meta directory ./fifo/.ts
Error listing meta directory ./dir/.ts
Error listing meta directory ./fifo/.ts
Error listing directory /mnt/test/loc/fifo
Directory index created . containing 4
Saving file: ./.ts/tsi.json
Index persisted for: . to ./.ts/tsi.json
Index generated in folder: .