related tdf#47471 textframe: use stylename if autostyle missing

The same fix for 47471 should also be useful for textframes.

Change-Id: I58b345eaa81dddf750f042610015ef45cd955c06
Reviewed-on: https://gerrit.libreoffice.org/65617
Tested-by: Jenkins
Reviewed-by: Justin Luth <justin_luth@sil.org>
diff --git a/xmloff/source/text/txtparae.cxx b/xmloff/source/text/txtparae.cxx
index 3d27ac0..5065fed 100644
--- a/xmloff/source/text/txtparae.cxx
+++ b/xmloff/source/text/txtparae.cxx
@@ -2913,10 +2913,11 @@
        rPropSet->getPropertyValue( gsFrameStyleName ) >>= sStyle;
    }

    OUString sAutoStyle( sStyle );
    OUString aMinHeightValue;
    OUString sMinWidthValue;
    sAutoStyle = Find( XML_STYLE_FAMILY_TEXT_FRAME, rPropSet, sStyle );
    OUString sAutoStyle = Find( XML_STYLE_FAMILY_TEXT_FRAME, rPropSet, sStyle );
    if ( sAutoStyle.isEmpty() )
        sAutoStyle = sStyle;
    if( !sAutoStyle.isEmpty() )
        GetExport().AddAttribute( XML_NAMESPACE_DRAW, XML_STYLE_NAME,
                              GetExport().EncodeStyleName( sAutoStyle ) );