Polygon permanently "Sketch" when closing window with "Esc"

[gaellafond]

When selection a polygon with the Plain Geometry Editor tool, and the checkbox "Sketch geometry" is checked, then the dialog window is closed using the "Esc" key, the polygon "blue" sketch do not go away.

• Selecting another polygon do not get rid of the previous "blue" sketch.
• Deselecting the Plain Geometry Editor tool do not get rid of the "blue" sketch.
• Deleting the polygon do not get rid of the "blue" sketch.
• Hiding the layer do not get rid of the "blue" sketch.
• Uninstalling / re-installing the Plain Geometry Editor tool do not get rid of the "blue" sketch.

NOTE: I was not aware that the blue fill was caused by the "Sketch" feature, so I called it "selection" in the screenshot.

The only way to get rid of the "blue" sketch is to quit and reload QGis.

[gaellafond]

I figure out that the "Sketch geometry" is what cause problem. Unchecking the checkbox prevent the tool from "painting" the polygon on the map with "permanent" paint.

If the polygon is already "painted", opening the polygon back with the tool and unchecking the checkbox do not get rid of the paint. The only way is to quit and reload QGis, so there is still a bug somewhere (maybe in QGis), but at least I have a workaround now.

[gaellafond]

Even more details:

The bug appear is I close the tool dialog window using the "Esc" key from the keyboard. There is no problem if I close the dialog window using "Alt+F4". There is no "close" button (or "X" button) on that dialog window (probably one of those strange Ubuntu decision), so the keyboard shortcut is the only way to close the window.

[EDIT] I found out I had a missing package. The "x" button is now showing. I have updated the issue title to illustrate the issue, not that I have narrowed it down.