Fix bug: once a witness is deemed invalid, no validator should overwrite the result
Fix bug: once a witness is deemed invalid, no validator should overwrite the result

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