title: Flutter does not apply firebase filter with integers
body: <p>I am trying to request data from firebase and apply filters using where and display them in a listView with help of Stream Builder. But the filters with an integer is not working and those with a string is working. I added a filter where the cost field has to be greater than 100, but it gives me all of them even if their cost is less. There is no error in the stacktrace. Here is the relevant code:-</p>
  <pre><code>StreamBuilder(
                  stream: Firestore.instance.collection(&quot;Planes&quot;).where(&quot;cost&quot;,isGreaterThan:100).snapshots(),//I have tried making 100 a string
                  builder: (context, snapshot) =&gt; ListView.builder(
                        itemCount: snapshot.data.documents.length,
                        itemBuilder: (context, index) {
                          return Padding(
                            padding: const EdgeInsets.symmetric(
                                vertical: 1.0, horizontal: 4.0),
                            child: Card(
                              child: ListTile(
                                onTap: () {
                                  Navigator.push(context, MaterialPageRoute(
                                  builder: (context) =&gt;
                                      ViewPlane(plane: snapshot,index:index,email: email,)));
                            },
                            leading: Icon(Icons.airplanemode_active),
                            title: Text(snapshot.data.documents[index][' destination']),
                            subtitle: Text(snapshot.data.documents[index]['airport']),
                          ),
                        ),
                      );
                    },
                  )
              ),
  </code></pre>
  <p>Any help will be appreciated<br />
  EDIT<br />
  Here is the image of database as per request
  <a href="https://i.stack.imgur.com/tVrih.jpg" rel="nofollow noreferrer">Dtabase image</a></p>