Infinite loop in `boundary_tracing()` — an interaction cap is missing

[glsch]

I've encountered an infinite loop in the boundary_tracing() function in kraken/lib/segmentation.py.

Tracing logic failed triggering the problem when the starting point could not be identified, I think because the region was defective (too small).

Interestingly, there's a counter variable inside the loop — but no actual check is implemented.

[glsch]

Possibly, this might mean that _extend_boundaries does not catch all possible problems, I have not investigated, though.

[mittagessen]

Do you have a sample I could reproduce the error with? From a cursory look the code has the proper termination conditions, there's just the superfluous counter variable.