The store owner wants to do something nice for people and in your world the best way to handle that is making them jump through months of bureaucracy and probably paying a lot of money to their insurance and for permits and shit?
Yeah, this attitude is why we can't have nice things and building anything costs a billion dollars.
Right, if that is really true as a blanket statement, then it's an idiotic and short sighted law.
I have a yard, plant a rose bush. You walk in the yard, bend down to smell the rose but lose balance, fall on the rose bush and the rose pokes your eye.
According to the rule, I'm not liable for your injury?
Besides being unfair and stupid, this sort of thing is actually costing society enormous amounts of lost effort, goodwill and actual money. How much time has been spent on bs court cases for things like I described? How much of a tax is liability insurance on everyone? How much fun things will never happen because of fear?
The store owner might also be required by the city and/or landlord to update their insurance policy to cover the extended liability.
But, in general, your proposed scenario never specified what the catastrophic event is and why the store owner would be held liable.