Fixed bug CORE-4319 : Engine crashes when trace config contains line "connection_id=NN" and we attempt to connect to non-existent database/alias

git-svn-id: svn+ssh://svn.code.sf.net/p/firebird/code/firebird/branches/B2_5_Release@59058 65644016-39b1-43b1-bf79-96bc8fe82c15