crashtesting: crash on exporting fdo31814-3.emf to odg

since

commit f9af0abce2
Date:   Sat Apr 15 01:44:46 2017 +0200

    EMF+ Add initial support for EmfPlusStringFormat Object

    The EmfPlusStringFormat object specifies text layout, display manipulations,
    and language identification. With this commit the support for font language
    and country was added. Also Bold style is applied,
    for strings which needs that.

elsewhere the pattern is to mask with 0xff to restrict to the hardcoded
256 size, so do that here too

Change-Id: Iba5bcc3fabe836c963b3eef47a864e87425675c7

cppcanvas/source/mtfrenderer/emfplus.cxx

@@ -1278,7 +1278,7 @@ namespace cppcanvas
 
                                 OUString text = read_uInt16s_ToOUString(rMF, stringLength);
 
-                                EMFPStringFormat *stringFormat = static_cast< EMFPStringFormat* >( aObjects[ formatId ] );
+                                EMFPStringFormat *stringFormat = static_cast< EMFPStringFormat* >( aObjects[ formatId & 0xff ] );
                                 css::rendering::FontRequest aFontRequest;
                                 LanguageTag aLanguageTag( static_cast< LanguageType >( stringFormat->language ) );
                                 aFontRequest.Locale = aLanguageTag.getLocale( false );