"Text formats" dialog shows modifiable buffer properties while the "draw text buffer" is unchecked

[DelazJ]

1. Open Style Manager, text format tab
2. Click + to add a new item
3. in the new dialog, browse the "Shadow", "Buffer", "Background" tabs; their properties are modifiable despite the top "Draw text XXX" is still unchecked.
4. If you were creating a "Label setting" item instead, you'd notice that the same properties are grayed until you check the "Draw text XXX" button

Wonder if it has to do with the non persistent labels background issue

QGIS a3f411a Windows 10

[DelazJ]

@elpaso, the shadow tab doesn't seem to be fixed, here with ea7b27e