title: Firefox browser.tabs.query({}).then() is undefined
body: <p>When I do <code>browser.tabs.query({"currentWindow": true, "active": true}).then(onCall, onError);</code> or <code>let querying = browser.tabs.query({"currentWindow": true, "active": true}); querying.then(onCall, onError);</code> in my addon's background script Firefox complains that </p>
  
  <pre><code>Unchecked lastError value: Error: browser.tabs.query(...) is undefined
  </code></pre>
  
  <p>When I replace the same line with the following, it will work as expected, although this is not mentioned in <a href="https://developer.mozilla.org/en-US/docs/Mozilla/Add-ons/WebExtensions/API/tabs/query" rel="nofollow noreferrer">Firefox API docs</a>:</p>
  
  <pre><code>browser.tabs.query({"currentWindow": true, "active": true}, function(tabs){
          onCall(tabs); 
        });
  </code></pre>
  
  <p>My Firefox version is 75.0 (64-bit) on Ubuntu.</p>
  
  <p>Is this a bug, or am I doing something wrong?</p>