Font size settings in buttons created by using template not displayed correctly

To reproduce:

1. Select File > New File or Project > Files and Classes > Qt Quick Controls > Custom Button > Choose.
2. Select Master > textItem, and set the button font to 12 pixels in the properties.
3. The values are changed in code and visible in the text editor, but the values in the properties field are arbitrary (for example, 9 points).

Sometimes this results in a syntax error that can be fixed by removing the "font: Constants.font" line, sometimes it works.