Miss case

lib/src/widgets/controller.dart

@@ -152,7 +152,9 @@ class QuillController extends ChangeNotifier {
       } else if (indent.value == 1 && !isIncrease) {
         formatAttribute = Attribute.clone(Attribute.indentL1, null);
       } else if (isIncrease) {
+        if (indent.value < 5) {
           formatAttribute = Attribute.getIndentLevel(indent.value + 1);
+        }
       } else {
         formatAttribute = Attribute.getIndentLevel(indent.value - 1);
       }