remove (<invalid_name>@<invalid_version>) from cmder promt when there is no name and version field in your package.json file

npm.lua

function npm_prompt_filter()
    local package = io.open('package.json')
    if package ~= nil then
        local package_info = package:read('*a')
        package:close()
        local package_name = string.match(package_info, '"name"%s*:%s*"(.-)"')
            or ""

        local package_version = string.match(package_info, '"version"%s*:%s*"(.-)"')
            or ""

        if package_name == "" and package_version == "" then
            local package_string = ""
        else
            local package_string = color.color_text("("..package_name.."@"..package_version..")", color.YELLOW)
            clink.prompt.value = clink.prompt.value:gsub('{git}', '{git} '..package_string)
        end

    end
    return false
end

Nice work :) Consider a pull request.