If the variable does not exist, just return.
[wine] / dlls / msisys / msisys.ocx.spec
2003-07-30  Alexandre JulliardMake the DllRegisterServer, DllRegisterServerEx, DllUnr...
2002-11-04  Alexandre JulliardMade the dll entry point default to DllMain and removed...
2002-06-21  Alexandre JulliardMade some more spec file entries optional or unnecessary.
2002-05-14  Alexandre JulliardAdded winebuild support for generating a .dbg.c file...
2002-05-09  Alexandre JulliardMoved imports specification from the .spec into the...
2002-04-08  Mike McCormackCreated a stubbed version of MSISYS.OCX.