Allow empty tokens in strict grammar

In SQLiteQueryBuilder, allow empty tokens when checking for invalid
tokens during the strict grammar check.

Fixes: 151151800
Fixes: 161769478
Test: atest SQLiteQueryBuilderTest#testStrictQueryEmptyToken
Change-Id: Iac1cdd643253fd186a164b863d65d6e92698fd38
(cherry picked from commit e409ec24)