fix crash on Windows on assert enabled builds

regression from
    commit 9cceba9a
    make DBG_TESTSOLARMUTEX available in assert builds

Change-Id: Ifbedc3c16f341a12ba026fc598fb5386da91c50c
Reviewed-on: https://gerrit.libreoffice.org/59245
Tested-by: Jenkins
Reviewed-by: Noel Grandin <noel.grandin@collabora.co.uk>

vcl/source/app/svmain.cxx

@@ -493,7 +493,7 @@ void DeInitVCL()
     }
     pSVData->mpDefaultWin.disposeAndClear();
 
-#ifdef DBG_UTIL
+#ifndef NDEBUG
     DbgGUIDeInitSolarMutexCheck();
 #endif