Why kernel quits when trying to FullSimplify Piecewise with default Nothing value?

I found that kernel of

    In[1]=$Version
(*"12.1.1 for Linux x86 (64-bit) (June 19, 2020)"*)

quits when trying to FullSimplify a simple piecewise function

Piecewise[{{0,  s == 0}}, Nothing]
FullSimplify[%]
(* kernel quit*)

Simple bug or invalid syntax?