This question is a continuation of Unprepared and Without a Homeworld.
The premise of this idea is that a substance called an Atomic Catalyst exists that can lower the temperature at which particles in contact with it can undergo fusion by a factor of ~10,000:1 so that Hydrogen fuses at ~1,300K, Helium at ~10,000K, etc. The catalyst itself is very stable such that it is not destroyed/consumed by the reactions that it triggers.
The Question:
Suspending disbelief that such a substance might exist to begin with, could it accidentally create a world-ending event?