Call gsf_shutdown in MsiCloseAllHandles to prevent DLL unload crash

After closing all handles and unreffing GLib objects, call gsf_shutdown()
to properly tear down libgsf. This preempts the crash that occurs when
libgsf's DllMain tries to clean up during DLL_PROCESS_DETACH after the
GLib type system is partially torn down.

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

Author: caesay

msi-interop/handle_table.c

@@ -299,6 +299,10 @@ handle_table_close_all(void)
     }
     g_free(to_unref);
 
+    // Shut down libgsf to prevent crashes during DLL unload.
+    // Must be called after all GsfInput/GsfOutput objects are freed.
+    gsf_shutdown();
+
     return count;
 }