Assert panic on dragging tab change its layer_id with egui extra_asserts feature turned on

[enomado]

Describe the bug
panicked at 'Widget changed layer_id during the frame'

To Reproduce
enable egui extra_asserts feature
start dragging some tab
asserting triggers in
/egui_dock-0.12.0/src/widgets/dock_area/show/leaf.rs:259:32

Additional context
Probably this is absolutely normal, but may be not )