include empty intermediary tables in optimized get

include empty intermediary tables in optimized get

Fixed issue in joined-inheritance load of additional attributes
functionality in deep multi-level inheritance where an intermediary table
that contained no columns would not be included in the tables joined,
instead linking those tables to their primary key identifiers. While this
works fine, it nonetheless in 1.4 began producing the cartesian product
compiler warning. The logic has been changed so that these intermediary
tables are included regardless. While this does include additional tables
in the query that are not technically necessary, this only occurs for the
highly unusual case of deep 3+ level inheritance with intermediary tables
that have no non primary key columns, potential performance impact is
therefore expected to be negligible.

Fixes: #7507
Change-Id: Id2073773e97a0853b744b51feeb2bc4437032e51
(cherry picked from commit c1d2fbac4c399b47f4715f7ea2a1147374d2aa43)