Revert code as it was in FB1.5 (PVS-Studio).

git-svn-id: svn+ssh://svn.code.sf.net/p/firebird/code/firebird/branches/B2_5_Release@59156 65644016-39b1-43b1-bf79-96bc8fe82c15
This bug comes from IB, maybe from the dawn of time (PVS-Studio).

git-svn-id: svn+ssh://svn.code.sf.net/p/firebird/code/firebird/branches/B2_5_Release@59157 65644016-39b1-43b1-bf79-96bc8fe82c15