The owners of all property responsible for repairing sidewalks as provided by this chapter shall be liable in damages to individuals injured because of any negligence of the owners in failing to keep a sidewalk in good condition. No liability shall be imputed to or imposed upon the city, its officers or employees because of injuries sustained by any person by reason of any defect in any sidewalk; nor because of any extension of time having been granted by the City Council for repairing any defects in sidewalks.