No, but it won't meltdown, it just stops lighting anymore. If the fan stops, then the LED will fail as soon as the heatsink gets too hot, which may be 10 minutes, or never.
Hi-power LEDs have a limited life, anywhere between 5,000 hours and 50,000 hours, depending mostly on the temperature of the silicon chip. As they age, they gradually get dimmer (after about 30,000 hours). Cooler is better, hence the fan.
I know I asked this before, but would it be beneficial to introduce some louvers to the back of the bucket? The back of the neat sink is actually the intake for the fan which blows forward over the back of the reflector. It does not cool the LEDs, only the heat sink.
(I always have wanted something with a cool set of louvers . . .)