Hi @flatKAT ,
I believe what I was doing in a similar situation was to call get_material of the static mesh in a while loop as long as the get_material() returned a material (i.e. not None). This way I was counting the material slots until get_material ()returned None in which case I knew there are no more material slots.
I am not sure if my approach works with fbx that were imported without materials, though.
Out of interest: Could you share the snippet of how you import an fbx without material?
Thank you.
-T