fix scroll to bottom button

lib/src/message_list_view.dart

@@ -309,19 +309,8 @@ class _MessageListViewState extends State<MessageListView> {
                   return messageWidget;
                 },
               ),
-              if (streamChannel.channel.state.members.contains((Member e) =>
+              if (widget.showScrollToBottom && _showScrollToBottom)
-                      e.userId == streamChannel.channel.client.state.user.id) &&
+                _buildScrollToBottom(),
-                  widget.showScrollToBottom)
-                StreamBuilder<int>(
-                    stream: streamChannel.channel.state.unreadCountStream,
-                    builder: (context, snapshot) {
-                      if (!_showScrollToBottom ||
-                          !snapshot.hasData ||
-                          snapshot.data == 0) {
-                        return SizedBox();
-                      }
-                      return _buildScrollToBottom(snapshot.data);
-                    }),
               Positioned(
                 top: 20.0,
                 child: ValueListenableBuilder<Iterable<ItemPosition>>(
@@ -364,7 +353,8 @@ class _MessageListViewState extends State<MessageListView> {
             position.itemLeadingEdge > max.itemLeadingEdge ? position : max);
   }
 
-  Widget _buildScrollToBottom(int unreadCount) {
+  Widget _buildScrollToBottom() {
+    final streamChannel = StreamChannel.of(context);
     return Positioned(
       bottom: 8,
       right: 8,
@@ -389,7 +379,16 @@ class _MessageListViewState extends State<MessageListView> {
               );
             },
           ),
-          Positioned(
+          if (streamChannel.channel.state.members.any((Member e) =>
+              e.userId == streamChannel.channel.client.state.user.id))
+            StreamBuilder<int>(
+                stream: streamChannel.channel.state.unreadCountStream,
+                initialData: streamChannel.channel.state.unreadCount,
+                builder: (context, snapshot) {
+                  if (!snapshot.hasData || snapshot.data <= 0) {
+                    return Offstage();
+                  }
+                  return Positioned(
                     width: 20,
                     height: 20,
                     left: 10,
@@ -398,7 +397,7 @@ class _MessageListViewState extends State<MessageListView> {
                       child: Padding(
                         padding: const EdgeInsets.all(3.0),
                         child: Text(
-                  unreadCount.toString(),
+                          snapshot.data.toString(),
                           style: TextStyle(
                             fontSize: 11,
                             fontWeight: FontWeight.bold,
@@ -406,7 +405,8 @@ class _MessageListViewState extends State<MessageListView> {
                         ),
                       ),
                     ),
-          ),
+                  );
+                }),
         ],
       ),
     );