Is the story of Imam Al-Nawawi, which includes the Sultan seeing him in the image of a lion when he intended to kill him, authentic, and is it considered a miracle for him indicating that he is upon the truth?

The story mentioned about Imam Al-Nawawi with Al-Zahir Baybars has not been found in the available references, nor has it been authenticated by any reliable scholars. Allah may bestow upon His righteous (pious believers) saints a miracle that confirms they are upon the truth.