title: Bundler & Minifier generating "Object reference not set to an instance of an object" error
body: <p>I trying bundle and minify my CSS and JS files in ASP.NET Core 3.0 with <code>BuildBundlerMinifier.Core</code>.
  Also Installed <code>Bundler &amp; Minifier</code> extension for Visual Studio 2019.</p>
  
  <p>When I try Debug the project, it working correctly without error but when I rebuild it, I'm getting the following error;</p>
  
  <blockquote>
    <p>Object reference not set to an instance of an object</p>
  </blockquote>
  
  <p><a href="https://i.stack.imgur.com/sO5oC.png" rel="noreferrer"><img src="https://i.stack.imgur.com/sO5oC.png" alt="enter image description here"></a></p>
  
  <p>I don't get an error when restart Visual Studio and I can debug the project again but If I rebuild it again, I'm getting the error.</p>
  
  <p>It's <code>bundleconfig.json</code> file</p>
  
  <pre><code>[
    {
      "outputFileName": "wwwroot/assets/css/style.bundle.min.css",
      "inputFiles": [
        "wwwroot/assets/plugins/global/plugins.bundle.css",
        "wwwroot/assets/css/style.bundle.css",
        "wwwroot/assets/css/skins/header/base/light.css",
        "wwwroot/assets/css/skins/header/menu/light.css",
        "wwwroot/assets/css/skins/brand/light.css"
      ],
      "sourceMap": false,
      "sourceMapRootPath": null
    }
  ,
  {
    "outputFileName": "wwwroot/assets/js/scripts.min.js",
    "inputFiles": [
      "wwwroot/assets/plugins/global/plugins.bundle.js",
      "wwwroot/assets/js/scripts.js",
      "wwwroot/assets/js/pages/dashboard.js",
      "wwwroot/content/js/mobil-detect.js",
      "wwwroot/content/js/lazy-img.js",
      "wwwroot/content/js/ziyaretci.js"
    ]
  }
  ]
  </code></pre>
  
  <p><a href="https://i.stack.imgur.com/XDVUN.png" rel="noreferrer"><img src="https://i.stack.imgur.com/XDVUN.png" alt="enter image description here"></a></p>
  
  <p>Visual Studio, Bundler &amp; Minifier extension, BuildBundlerMinifier and BuildBundlerMinifier.Core are up to date
  How can I fix it ?</p>