Issues with texture randomizing

[mphe]

See #155 (comment)

1. Edges randomly disappear if distance between points is too small
   • Only happens on master branch, not on current stable release in Asset Library. That means, the regressions happened between e8eb802 and 813f1b2.
   • Workaround: Increase the distance between points.
2. Textures change with each reload
   • It might be desirable to not re-randomize on each load.
   • One could add a seed property to SS2D_Shape to keep the randomization reproducible.

[limbonaut]

Could be related to issue mentioned here #156 (comment)
However, I managed to reproduce that issue in v3.0.0 as well, so maybe it's a different bug.

Reproduction: reproduction_edge_vanish.zip

EDIT: updated reproduction project - unpack into project's root