Remove events in the latest leaflet build

Since Leaflet/Leaflet@a1acaffdf1e0f0598932c559b13473e892d8544b there are two more conditions added in the last if-statement removeEventListener function. When the contextId is undefined the events won't be removed. It should be solved by passing the marker its context to the off calls in the removeHooks. 

```javascript
removeHooks: function () {
		L.Draw.Feature.prototype.removeHooks.call(this);

		if (this._map) {
			if (this._marker) {
				this._marker.off('click', this._onClick, this);
				this._map
					.off('click', this._onClick, this)
					.removeLayer(this._marker);
				delete this._marker;
			}

			this._mouseMarker.off('click', this._onClick, this);
			this._map.removeLayer(this._mouseMarker);
			delete this._mouseMarker;

			this._map.off('mousemove', this._onMouseMove, this);
		}
	}
```

EDIT: besides Draw.Marker the similar problem also existed in Draw.PolyLine, EditToolbar.Delete and EditToolbar.Edit