daemon legacy pak empty version string

// ==== Daemon:src/common/FileSystem.cpp ====

// Pak zip and directory extensions
#define LEGACY_PAK_ZIP_EXT ".pk3"
#define LEGACY_PAK_DIR_EXT ".pk3dir/"
#define PAK_ZIP_EXT ".dpk"
#define PAK_DIR_EXT ".dpkdir/"

// Add a pak to the list of available paks
static void AddPak(pakType_t type, Str::StringRef filename, Str::StringRef basePath)
{
    std::string fullPath = Path::Build(basePath, filename);

    if (!UseLegacyPaks()) {
        size_t suffixLen = type == pakType_t::PAK_DIR ? strlen(PAK_DIR_EXT) : strlen(PAK_ZIP_EXT);
    } else {
        size_t suffixLen = type == pakType_t::PAK_DIR ? strlen(LEGACY_PAK_DIR_EXT) : strlen(LEGACY_PAK_ZIP_EXT);
    }
    std::string name, version;
    Util::optional<uint32_t> checksum;
    if (!ParsePakName(filename.begin(), filename.end() - suffixLen, name, version, checksum) || (type == pakType_t::PAK_DIR && checksum)) {
        if (!UseLegacyPaks()) {
            fsLogs.Warn("Invalid pak name: %s", fullPath);
            return;
        } else {
            fsLogs.Notice("Loading legacy pak: %s", fullPath);
            name = filename.substr(0, filename.size() - suffixLen);
            // prefer versioned dpk over legacy pk3 if pak name collides, uses the smallest version string available
            // this version can't be found in standard dpk, so we can also uses this value to test later if it's a legacy pk3
            version = "";
        }
    }

    availablePaks.push_back({std::move(name), std::move(version), checksum, type, std::move(fullPath)});
}

// ==== Daemon:src/engine/server/sv_client.cpp ====

/*
==================
SV_WriteDownloadToClient

Check to see if the client wants a file, open it if needed and start pumping the client
Fill up msg with data
==================
*/
void SV_WriteDownloadToClient( client_t *cl, msg_t *msg )
{
…
            if ( version.compare("") == 0 ) {
                // legacy pak
                std::string pakName = name + ".pk3";
            } else {
                // versionned pak
                std::string pakName = name + "_" + version + ".dpk";
            }
…
}