title: The getter 'length' was called on snapshot's data
body: <p>When the app starts it throws an Exception caught by widgets library in a console:</p>
  <pre><code>======== Exception caught by widgets library ======================================================= The following NoSuchMethodError was thrown building
  StreamBuilder&lt;List&lt;Entry&gt;&gt;(dirty, state:
  _StreamBuilderBaseState&lt;List&lt;Entry&gt;, AsyncSnapshot&lt;List&lt;Entry&gt;&gt;&gt;#97504): The getter 'length' was called on
  null. Receiver: null Tried calling: length on `itemCount: snapshot.data.length`, 
  </code></pre>
  <p>But the whole app nonetheless works in emulator. What is the reason of that?</p>
  <pre><code>StreamBuilder&lt;List&lt;Entry&gt;&gt;(
            stream: entryProvider.entries,
            builder: (context, snapshot) {
              return ListView.builder(
                  itemCount: snapshot.data.length, // the error is here
                  itemBuilder: (context, index) { ...
  </code></pre>