tdf#91726: AutoFormat: Crash when using an existing name

Add a test to check if name already exists

Change-Id: Ie23de04c0b747f58ab61a6e498bf212bf38b346a
Reviewed-on: https://gerrit.libreoffice.org/16000Reviewed-by: Caolán McNamara <caolanm@redhat.com>
Tested-by: Caolán McNamara <caolanm@redhat.com>

sc/source/ui/miscdlgs/scuiautofmt.cxx

@@ -233,7 +233,7 @@ IMPL_LINK_NOARG(ScAutoFormatDlg, AddHdl)
             {
                 aFormatName = pDlg->GetInputString();
 
-                if ( !aFormatName.isEmpty() && !aFormatName.equals(aStrStandard) )
+                if ( !aFormatName.isEmpty() && !aFormatName.equals(aStrStandard) && pFormat->find(aFormatName) == pFormat->end() )
                 {
                     ScAutoFormatData* pNewData
                         = new ScAutoFormatData( *pSelFmtData );