Return error instead of unknown by default
Return error instead of unknown by default

ultimate-pa/benchexec,ultimate-pa/benchexec,sosy-lab/benchexec,ultimate-pa/benchexec,ultimate-pa/benchexec,ultimate-pa/benchexec,sosy-lab/benchexec,ultimate-pa/benchexec,sosy-lab/benchexec,sosy-lab/benchexec,sosy-lab/benchexec,sosy-lab/benchexec