For the purposes of this subchapter, it shall not be essential that the nuisance be created or contributed to by the owner, occupant or person having control or management of the premises, but merely that the nuisance is created or contributed to by licensees, invitees, guests or other persons for whose conduct the owner or operator is responsible, or by persons for whose conduct the owner or operator is not responsible, but by the exercise of reasonable care ought to have become aware of.