make 'try0' return faster when invoked as part of 'try'
make 'try0' return faster when invoked as part of 'try'

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