uxtheme: Return NULL file handle on OpenThemeFile() failure.

Signed-off-by: Nikolay Sivov <nsivov@codeweavers.com>
Signed-off-by: Alexandre Julliard <julliard@winehq.org>

dlls/uxtheme/msstyles.c

@@ -188,6 +188,7 @@ HRESULT MSSTYLES_OpenThemeFile(LPCWSTR lpThemeFile, LPCWSTR pszColorName, LPCWST
     return S_OK;
 
 invalid_theme:
+    *tf = NULL;
     if(hTheme) FreeLibrary(hTheme);
     return hr;
 }