Attempts to Commit Offences
Abetting an imprisonment-punishable offence, if not committed and no other punishment is specified, is punished with up to one-fourth of the offence's longest imprisonment term (or its fine, or both) - rising to up to one-half if the abettor or the abetted person is a public servant duty-bound to prevent that offence.
This sets the default abetment punishment (a fraction of the underlying offence's sentence) for less serious imprisonment-only offences, with an enhanced penalty specifically for public servants who abet crimes they're supposed to be preventing - like a police officer who helps enable an offence rather than stopping it.
A police officer whose duty is to prevent robbery, who instead abets a robbery that doesn't ultimately occur, faces up to half the maximum robbery sentence for that abetment - a harsher penalty than an ordinary citizen would face for the same abetment.