[Therion] Length of cave reported too much by factor of 150 times

Somewhere between Therion 6.3.1 and 6.3.4 my cave model grew from about 38 km in length to 5,727 km in length. The shorter distance is more likely to be correct! I presume it is a Therion bug rather than a bug in my data input. I have described it a little more in https://github.com/therion/therion/issues/663 Bruce