LONDON -- Stella Tennant, the aristocratic British model who was a muse to designers such as Karl Lagerfeld and Gianni Versace, has died suddenly at the age of 50, her family said Wednesday.Tennant, the granddaughter of a duke, rose to fame in the 1990s while walking the runway for designers including Versace and Alexander McQueen.In a statement, her family said: “It is with great sadness we announce the sudden death of Stella Tennant on Dec.