It's better to always check isql return code

git-svn-id: svn+ssh://svn.code.sf.net/p/firebird/code/firebird/trunk@58812 65644016-39b1-43b1-bf79-96bc8fe82c15
Use better way to ignore unused return value - thanks to Adriano

git-svn-id: svn+ssh://svn.code.sf.net/p/firebird/code/firebird/trunk@58813 65644016-39b1-43b1-bf79-96bc8fe82c15