retain isolated blob nodes (amending deb2fcbda16e): avoid failure of Session.handle_change with "Missing blob", when opening theory with load command later;
theory Quickcheck_Nesting_Example
imports Quickcheck_Nesting
begin
datatype x = X "x list"
lemma "X a = X b"
quickcheck[exhaustive, size = 4, expect = counterexample]
oops
end