your testimg routine is called from a for mat in mats:   do you have 14 materials in that figure ?

I would say when your else clause executes then your fault occurs. If you have corrected the logic to get the node input innode you also need to account for each input in the node.

 

for example a blender node may be connected to the diffuse color input, blender node has three inputs, so an image map may be logged into one , two or all three inputs.

example skin image map to input 1, tatoo image map to input 2 and a mask image to input 3.

I have no idea how you sort that out :-(  

remember though you can build a list of nodes and then go back and work through the list.

 

could you post you script again ? attach a copy as a txt file would be fine.