fix _keyboardHeight

packages/zefyr/lib/src/widgets/toolbar.dart

 
   @override
   Widget build(BuildContext context) {
-    if (editor.toolbarAction == null) {
+    if (editor.toolbarAction == null && _keyboardHeight != MediaQuery.of(context).viewInsets.bottom) {
       _keyboardHeight = MediaQuery.of(context).viewInsets.bottom;
     }
     final theme = ZefyrTheme.of(context).toolbarTheme;