msi: Don't bother to unregister classes at process exit.

dlls/msi/msi_main.c

@@ -76,6 +76,7 @@ BOOL WINAPI DllMain(HINSTANCE hinstDLL, DWORD fdwReason, LPVOID lpvReserved)
         IsWow64Process( GetCurrentProcess(), &is_wow64 );
         break;
     case DLL_PROCESS_DETACH:
+        if (lpvReserved) break;
         msi_dialog_unregister_class();
         msi_free_handle_table();
         msi_free( gszLogFile );