add protection in StackTrace() against gApplication being 0.

git-svn-id: http://root.cern.ch/svn/root/trunk@34174 27541ba8-7e3a-0410-8455-c3a389f83636

core/unix/src/TUnixSystem.cxx

@@ -2071,7 +2071,7 @@ void TUnixSystem::StackTrace()
 
    if (fd && message) { }  // remove unused warning (remove later)
 
-   if (!strcmp(gApplication->GetName(), "TRint"))
+   if (gApplication && !strcmp(gApplication->GetName(), "TRint"))
       Getlinem(kCleanUp, 0);
 
 #if defined(USE_GDB_STACK_TRACE)