title: Why does add-on icon disappear, if install.rdf is present?
body: <p>After I’ve install my add-on I don’t see the toolbar icon in Firefox.
  I’ve faced this issue during development. If <a href="https://developer.mozilla.org/en-US/Add-ons/Install_Manifests" rel="nofollow"><code>install.rdf</code></a> file is present, the add-on’s icon does not appear in the Firefox toolbar. However, it works absolutely fine without an <code>install.rdf</code> file. What is wrong?</p>
  
  <pre><code>&lt;?xml version="1.0" encoding="UTF-8"?&gt;
  
  &lt;RDF xmlns="http://www.w3.org/1999/02/22-rdf-syntax-ns#"
       xmlns:em="http://www.mozilla.org/2004/em-rdf#"&gt;
    &lt;Description about="urn:mozilla:install-manifest"&gt;
      &lt;em:id&gt;extensionName@myDomain.com&lt;/em:id&gt;
      &lt;em:version&gt;1.23&lt;/em:version&gt;
      &lt;em:type&gt;2&lt;/em:type&gt;
  
      &lt;em:targetApplication&gt;
        &lt;Description&gt;
          &lt;em:id&gt;{uuid here}&lt;/em:id&gt;
          &lt;em:minVersion&gt;31.*&lt;/em:minVersion&gt;
          &lt;em:maxVersion&gt;47.*&lt;/em:maxVersion&gt;
        &lt;/Description&gt;
      &lt;/em:targetApplication&gt;
  
      &lt;em:name&gt;extensionName&lt;/em:name&gt;
      &lt;em:description&gt;Lorem ipsum dolor sit amet, consectetur adipisicing elit. Veniam voluptates natus soluta quis culpa animi, vitae laborum magnam! Facere reiciendis nihil porro non odio hic deserunt obcaecati soluta, nostrum recusandae!&lt;/em:description&gt;
      &lt;em:creator&gt;Name LastName&lt;/em:creator&gt;
      &lt;em:homepageURL&gt;http://www.mydDomain.com/&lt;/em:homepageURL&gt;
    &lt;/Description&gt;
  &lt;/RDF&gt;
  </code></pre>