If things go as planned, then the length of the polygon is the same as the
number of rows in the model. Turns out when running Subsurface-mobile on
Android that simple truth doesn't seem to be correct. Most of the time
the polygon seems to have twice as many elements as the model. But a few
times I ended up in here with a polygon that had fewer elements than the
model. And then things crash.
This simply avoids the crash.
Signed-off-by: Dirk Hohndel <dirk@hohndel.org>
9dd26a00e8