rsdio tipped us to an app note on protecting a boost-converter LED driver :
Several circuit ideas are presented for protecting a boost-converter LED driver when the LEDs are disconnected. (Without protection, the driver output can destroy the external MOSFET and Schottky diode.) An LED-driver IC (MAX1698) and comparator (MAX9060 or MAX9028) are included.
If you hook the ground end of the zener up to the base of a transistor that’s setup to pull down the shutdown line of the converter, you can make this permanently safe from open-circuit arrays of high-power LEDs (in the normal configuration the zener would have to dissipate the full power of the LED array).