UltraLite does not process requests or queries referencing the index while the DROP INDEX statement is being processed. Furthermore,
you cannot execute DROP INDEX when the database includes active queries or uncommitted transactions.
Use the IF EXISTS clause if you do not want an error returned when the DROP INDEX statement attempts to remove an index that
does not exist.
When you specify the IF EXISTS clause and the named table cannot be located, an error is returned.
For UltraLite.NET users: You cannot execute this statement unless you also call the Dispose method for all data objects (for
example, ULDataReader). See Dispose method.