ntdll: Don't return a default Unix handle for modules that don't have a Unix library.

dlls/ntdll/unix/virtual.c

@@ -655,8 +655,11 @@ static NTSTATUS get_builtin_unix_funcs( void *module, BOOL wow, void **funcs )
     LIST_FOR_EACH_ENTRY( builtin, &builtin_modules, struct builtin_module, entry )
     {
         if (builtin->module != module) continue;
-        *funcs = dlsym( builtin->unix_handle, ptr_name );
-        status = *funcs ? STATUS_SUCCESS : STATUS_ENTRYPOINT_NOT_FOUND;
+        if (builtin->unix_handle)
+        {
+            *funcs = dlsym( builtin->unix_handle, ptr_name );
+            status = *funcs ? STATUS_SUCCESS : STATUS_ENTRYPOINT_NOT_FOUND;
+        }
         break;
     }
     server_leave_uninterrupted_section( &virtual_mutex, &sigset );