strange file association in Firefox when choosing “Open containing folder”

Question

When I download a file in Firefox and click "Open containing Folder" it opens the folder in Baobab instead of PCMan FM.

I don't know how I ended up with this behaviour; I want Firefox to open it in PCMan FM.

I'm running LXDE on Debian 10.0.

$ mimetype ~/Downloads
/home/milo/Downloads: inode/directory

$ grep directory /etc/mime.types 
#  file in their home directory.  Definitions included there will take
application/vnd.japannet-directory-service
application/vnd.noblenet-directory
inode/directory-locked
inode/directory
text/directory

$

Answer 1

mimeopen

$ mimeopen Downloads/
Please choose a default application for files of type inode/directory

    1) Disk Usage Analyzer  (org.gnome.baobab)
    2) File Manager PCManFM  (pcmanfm)
    3) Other...

use application #2
Opening "Downloads/" with File Manager PCManFM  (inode/directory)

$ cat .config/mimeapps.list 
[Default Applications]
inode/directory=pcmanfm.desktop;

The new config file is created which now defines a default application for folders.

Thanks to Frank Schrijver for pointing me in the right direction.