convertLanguageToLocale: last resort en-US if resolve requested

Change-Id: I8ebdfe34765292f14642ec8c2721621e5638a17a
diff --git a/i18nlangtag/source/isolang/mslangid.cxx b/i18nlangtag/source/isolang/mslangid.cxx
index 6e816ee..8f398e5 100644
--- a/i18nlangtag/source/isolang/mslangid.cxx
+++ b/i18nlangtag/source/isolang/mslangid.cxx
@@ -153,9 +153,17 @@ LanguageType MsLangId::resolveSystemLanguageByScriptType( LanguageType nLang, sa
    {
        // Still resolve LANGUAGE_DONTKNOW if resolving is not requested,
        // but not LANGUAGE_SYSTEM or others.
        LanguageType nOrigLang = nLang;
        if (bResolveSystem || nLang == LANGUAGE_DONTKNOW)
            nLang = MsLangId::getRealLanguage( nLang);
        convertLanguageToLocaleImpl( nLang, aLocale);
        if (bResolveSystem && aLocale.Language.isEmpty() && simplifySystemLanguages( nOrigLang) == LANGUAGE_SYSTEM)
        {
            // None found but resolve requested, last resort is "en-US".
            aLocale.Language = "en";
            aLocale.Country  = "US";
            aLocale.Variant  = OUString();
        }
    }
    return aLocale;
}