Low Description
If you have a secondary index implementation that 'indexes()' the cql3 row marker you get a NPE in SecondaryIndexManager/deleteFromIndexes() as the call to getColumnDefinitionFromColumnName() returns null which is not checked for.
This has been detected in the context of inserting PK only rows, where the row marker is expected to be present. When 'indexes()' returned 'false', the row would mistakenly get deleted as the row marker didn't go through.
If 'indexes()' returns 'true' the row marker goes through but you get a NPE.