Start now a new fact.
        clone_selected (bool): whether to start a clone of currently
            selected fact or to create a new fact from scratch.
        fallback (bool): if True, fall back to creating from scratch
                         in case of no selected fact.

def start_new_fact(self, clone_selected=True, fallback=True):
        """Start now a new fact.
        clone_selected (bool): whether to start a clone of currently
            selected fact or to create a new fact from scratch.
        fallback (bool): if True, fall back to creating from scratch
                         in case of no selected fact.
        """
        if not clone_selected:
            dialogs.edit.show(self, base_fact=None)
        elif self.fact_tree.current_fact or fallback:
            dialogs.edit.show(self, base_fact=self.fact_tree.current_fact)