Bugfixes and improvements

Bugfix: Crashes in multiple situations while typing
Bigfix: Invalid table or schema.table suggestion when ambiguous column
reference recognized but some of the source tables don't have alias or
there is conflict between logical and physical object names when
physical object specified with schema.
Bugfix: Invalid join condition suggestion when joined objects contain
columns without aliases
Improvement: Closing parenthesis ignored when extra entered after it was
automatically entered by the code completion