In the export_descr_unit.txt file (EDU) located in your data folder, you just need to remove the "slave" entry. That's not critical and you can leave it if you want.
In the battle_models.modeldb file located in the unit_models subfolder in the data folder, for Italian_Cavalry_Militia, you have originally:
Code:
5 slave
68 unit_models/sandy_units/AttachmentSets/gs_attachments_slave.texture
68 unit_models/sandy_units/AttachmentSets/gs_attachments_normal.texture 0
Replace the "68" in red by "67". You should get:
Code:
5 slave
67 unit_models/sandy_units/AttachmentSets/gs_attachments_slave.texture
68 unit_models/sandy_units/AttachmentSets/gs_attachments_normal.texture 0
Hope it helps.
Edit: check that carefully because unless you have already corrected it by yourself, it is 68 and not 67 for the "slave".