title: getString("android.text") returns SpannableString instead of String
body: <p>I'm trying to get notification content using:</p>
  <pre><code>val sender = sbn.notification.extras.getString(&quot;android.title&quot;)
  val msg = sbn.notification.extras.getString(&quot;android.text&quot;)
  </code></pre>
  <p><code>android.title</code> returns the desired value, but <code>android.text</code> returns <code>null</code>.</p>
  <p>Upon debugging, I found out:</p>
  <pre><code>W/Bundle: Key android.text expected String but value was a android.text.SpannableString. The default value &lt;null&gt; was returned.
  W/Bundle: Attempt to cast generated internal exception:
  java.lang.ClassCastException: android.text.SpannableString cannot be cast to java.lang.String
  </code></pre>
  <p>Why <code>android.text</code> is returning <code>SpannableString</code>? And how can I convert it to <code>String</code> in this case?</p>