title: UI-Router - query parameter not allowing array with single item
body: <p>I have an application using UI-Router. There is a <code>Widgets</code> state with one query parameter that accepts an array of widgets:</p>
  <pre><code>const widgetsState = { name: &quot;widgets&quot;, url: &quot;/widgets?{widgets:string[]}&quot;, component: Widgets, params: {
    widgets: {
      isArray: true,
      value: [],
    }
  } };
  </code></pre>
  <p>Routing to this state works with an empty array or an array with multiple items, but fails when given an array of just one item:</p>
  <pre><code>&lt;a uiSref=&quot;widgets&quot; [uiParams]=&quot;{ widgets: [] }&quot;&gt;Empty array - works fine&lt;/a&gt;
  &lt;a uiSref=&quot;widgets&quot; [uiParams]=&quot;{ widgets: ['foo'] }&quot;&gt;Single item - throws error!&lt;/a&gt;
  &lt;a uiSref=&quot;widgets&quot; [uiParams]=&quot;{ widgets: ['foo','bar'] }&quot;&gt;Multiple items - works fine&lt;/a&gt;
  </code></pre>
  <p>When routing with just a single item in the array, I get this error:</p>
  <blockquote>
  <p>This transition is invalid, detail: The following parameter values are not valid for state 'widgets': [widgets:&quot;foo&quot;]))</p>
  </blockquote>
  <p><strong>How can I get UI-Router to allow an array containing a single item to be passed in as a parameter?</strong></p>
  <p>This <a href="https://stackblitz.com/edit/uirouter-angular-hello-world-nwxubm" rel="nofollow noreferrer">Stackblitz demo</a> shows a minimal reproduction of the error.</p>
  <p>I've noticed that if I remove the parameter from the url, it will properly handle arrays of single items. However I need to retain the ability to deep-link with these parameters, so that's not an option for my application.</p>