title: Npm string empty when Etherpad is loaded as Service
body: <p>today Iam trying to get an Etherpad Instance working as a Service.</p>
  <p>The Installation and configuration of the Etherpad is fine. Everything works well if I start the Etherpad myself.</p>
  <p>But I want to get this running as a Service on autostart.</p>
  <p>The Etherpad wont start due to the following Error:</p>
  <pre><code> Abort trap
   ERROR: Cannot extract npm major version from version string &quot;&quot;
   [: : bad number
   [: : bad number
   ERROR: Your npm version &quot;.&quot; is too old. npm 5..x or higher is required.
    1: 0x16adf70 node::Abort(void) [/usr/local/bin/node]
    2: 0x16811da node::PlatformInit(void) [/usr/local/bin/node]
    3: 0x16801a0 node::InitializeOncePerProcess(int, char**) [/usr/local/bin/node]
    4: 0x1680779 node::Start(int, char**) [/usr/local/bin/node]
  </code></pre>
  <p>Any tips?</p>
  <p>Edit:</p>
  <p>Iam using the following Versions:</p>
  <ul>
  <li>Etherpad: git master</li>
  <li>npm 6.14.8</li>
  <li>nodejs 15.6.0</li>
  </ul>