Fixed 2.5.3 regression, introduced by one of my previous commits - deadlock when starting transaction using SQL operator

git-svn-id: svn+ssh://svn.code.sf.net/p/firebird/code/firebird/branches/B2_5_Release@58606 65644016-39b1-43b1-bf79-96bc8fe82c15
Fixed bug CORE-3921 : "record disappeared (186), file: vio.cpp line: 408"

git-svn-id: svn+ssh://svn.code.sf.net/p/firebird/code/firebird/branches/B2_5_Release@58610 65644016-39b1-43b1-bf79-96bc8fe82c15