made (co)rec tactic more robust when the simplifier succeeds early
made (co)rec tactic more robust when the simplifier succeeds early

MerelyAPseudonym/isabelle,MerelyAPseudonym/isabelle,MerelyAPseudonym/isabelle,MerelyAPseudonym/isabelle,MerelyAPseudonym/isabelle,MerelyAPseudonym/isabelle