message: Fix impossibility of deleting the last extractor
  Fix broken LegacyExtractorsDB::Write() implementation to allow deleting
  _all_ extractors. This was a non-issue in previous versions where such
  situation was pointless, but with Poedit 2's builtin extractors, this
  can actually be pretty common.
diff: @@ -84,28 +84,28 @@ void LegacyExtractorsDB::Read(wxConfigBase *cfg)
  void LegacyExtractorsDB::Write(wxConfigBase *cfg)
  {
  #if 0 // asserts on wxGTK, some bug in wx
  - if (cfg->HasGroup("Parsers"))
  - cfg->DeleteGroup("Parsers");
  + if (cfg->HasGroup("/Parsers"))
  + cfg->DeleteGroup("/Parsers");
  #endif
  cfg->SetExpandEnvVars(false);
  - if (Data.empty())
  - return;
  -
  size_t i;
  wxString list;
  + if (!Data.empty())
  + {
  list << Data[0].Name;
  for (i = 1; i < Data.size(); i++)
  list << ";" << Data[i].Name;
  - cfg->Write("Parsers/List", list);
  + }
  + cfg->Write("/Parsers/List", list);
  wxString oldpath = cfg->GetPath();
  wxString key;
  for (const auto& item: Data)
  {
  key = item.Name; key.Replace("/", "_");
  - cfg->SetPath("Parsers/" + key);
  + cfg->SetPath("/Parsers/" + key);
  cfg->Write("Enabled", item.Enabled);
  cfg->Write("Extensions", item.Extensions);
  cfg->Write("Command", item.Command);
  