`UI_OT_button_string_clear` clears the redo panel in `wm_operator_finished`.
hud_status is set to CLEAR due to undo flag on above the internal operator.
To fix the redo panel from closing, undo flag from the operator could be
removed. Alternative is, skip internal operators from closing the redo
panel with extra check `if (op->type->flag & OPTYPE_INTERNAL) {return;}`
Ref: !135727