This tassert in index_bounds_builder.cpp is not particularly useful for diagnosing issues since it doesn't indicate what type of geometry we're using. In other words, how did we end up with a geometry that doesn't have an S2 region? it may even be possible that this is a user error (providing a geometry type that's inappropriate for $geoWithin) that managed to make it that far.

We should improve that log line to shed some insight on the geometry in question, and while we're at it should audit other loglines related to geometry containers with more detail to help diagnose issues.