The internals of `newSeriesCursor` returned a struct pointer that
implicitly got turned into the interface. Unfortunately, Go treats this
type of interface conversion as a nil pointer to the struct rather than
as just nil so if you attempted to compare the returned cursor to nil,
they would not be equal and it would think it was non-nil and attempt to
use the cursor.
Stuart Carnie
Mark Rushakoff
Jonathan A. Sternberg
Stuart Carnie