fix unread indicator

lib/src/unread_indicator.dart

@@ -12,12 +12,17 @@ class UnreadIndicator extends StatelessWidget {
 
   @override
   Widget build(BuildContext context) {
-    return Padding(
-      padding: const EdgeInsets.only(left: 8.0),
-      child: CircleAvatar(
-        backgroundColor:
-            StreamChatTheme.of(context).channelPreviewTheme.unreadCounterColor,
-        radius: 8,
+    return Material(
+      borderRadius: BorderRadius.circular(8),
+      color: StreamChatTheme.of(context).channelPreviewTheme.unreadCounterColor,
+      child: Padding(
+        padding: const EdgeInsets.only(
+          left: 5.0,
+          right: 5.0,
+          top: 2,
+          bottom: 1,
+        ),
+        child: Center(
           child: Text(
             '${channel.state.unreadCount}',
             style: TextStyle(
@@ -26,6 +31,7 @@ class UnreadIndicator extends StatelessWidget {
             ),
           ),
         ),
+      ),
     );
   }
 }