robbery with a dangerous weapon; fatal variance argument not preserved for appellate review; evidence of dangerousness required to support submission of robbery with a dangerous weapon charge to jury; evidence that gun was inoperable or non-deadly insufficient on its own to establish dangerousness of gun; absence of evidence of dangerousness of inoperable or non-deadly gun required dismissal of robbery with a dangerous weapon charge; improper judicial comment on the evidence; prejudice showing not met by judicial comment on the evidence; no record of required habitual felon colloquy required remand for habitual felon colloquy or proof of habitual felon status