advpack: DelDirs should only remove a directory if it's empty.

dlls/advpack/install.c

diff --git a/dlls/advpack/install.c b/dlls/advpack/install.c
index 544915d..2feadee 100644
--- a/dlls/advpack/install.c
+++ b/dlls/advpack/install.c
@@ -87,7 +87,7 @@
                                MAX_INF_STRING_LENGTH, &size))
             continue;
 
-        if (DelNodeW(directory, 0))
+        if (DelNodeW(directory, ADN_DEL_IF_EMPTY))
             hr = E_FAIL;
     }