Mark (like backslash) appearing in middle of freehand shape

I created a freehand shape copied in the attached document. At some point, a short line, like [ \ ], appeared in the exact middle of it, and I don’t know how to make it go away. The yellow area color is just to make it show up; it’s the same whether using a gradient or even a bitmap. I thought it might just be a formatting mark, but it appears in print preview, too. What is this and how can I fix it?

mark-in-shape.odt

Double-click on your shape. A blinking cursor will appear after your backslash. Hit Backspace, this will erase the character. Click anywhere outside the image, you’re done.

Explanation

Every shape or graphic object may be labeled. By default, this label is attached to the center of rectangle enclosing the object. At some point in your editing, you triggered unwittingly the creation of this label.

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