Tabs' label look incorrect when dragging for rearranging (Also valid on the editor)

[gongpha]

Godot version:

Master Branch 8c045fc

OS/device including version:

Windows 10 64-bit ( Vulkan )

Issue description:

TabContainer with "Drag to Rearrange Enabled" allows the user to drag its tabs by mouse to rearrange.

Steps to reproduce:
In the game :

1. Create TabContainer node with drag_to_rearrange_enabled is enabled
2. Create 2 tabs. Name it differently.
3. Put any Control nodes to tabs.
4. Put tabs inside TabContainer.
5. Run a game. And try to drag any tab to any position.
6. Problem arrived. Tab boxes and their contents changed. But their labels aren't.

In the editor :

1. Drag any tab in the editor to any position.
2. Problem arrived the same as the game.

( Sorry for the editor's language, which made you confused. I'm in a hurry )

Minimal reproduction project:

TabContainer.zip

[akien-mga]

CC @volzhs in case this is related to recent TabContainer fixes.

[gongpha]

Still valid in 0167bfa. Before his last commit on tab_container.cpp.