In Extended-format for booleans in grids, set fa fa-square-full| (with pipe ¦), because the first parameter will be used as filtering icon, when nothings is chosen for filtering.
Note
Defines the font-icons used for logical_filter columns. Pipe-separated list of font-icons: emptyIcon|trueIcon|falseIcon|nullIcon|filterTrueIcon|filterFalseIcon. Every icon is optional. "emptyIcon" is used for filtering.