Duplicated text editor in object editor when it contains velocity code

Reproduction steps:

• Login with Admin
• Access http://localhost:8080/xwiki/bin/edit/Panels/Children?editor=object
• Open the PanelClass xobject
• Check the Content field

Expected result:

• A text editor is displayed with syntax highlighting

Obtained result:

• Two identical editors are displayed one on top of the other: