Resolves: tdf#112827 gtk3 menubar not RTL under RTL locales

Change-Id: Icb2fa621e1f7da1e2d4bd221c8e1d8677cc956a2
Reviewed-on: https://gerrit.libreoffice.org/43057Tested-by: Jenkins <ci@libreoffice.org>
Reviewed-by: Caolán McNamara <caolanm@redhat.com>
Tested-by: Caolán McNamara <caolanm@redhat.com>

vcl/source/app/settings.cxx

@@ -2845,10 +2845,7 @@ namespace
 
         if( nUIMirroring == 0 )  // no config found (eg, setup) or default (nil) was set: check language
         {
-            LanguageType aLang = LANGUAGE_DONTKNOW;
-            ImplSVData* pSVData = ImplGetSVData();
-            if ( pSVData->maAppData.mpSettings )
-                aLang = pSVData->maAppData.mpSettings->GetUILanguageTag().getLanguageType();
+            LanguageType aLang = SvtSysLocaleOptions().GetRealUILanguageTag().getLanguageType();
             if (bMath)
                 bRTL = MsLangId::isRightToLeftMath( aLang );
             else