The Step Area series uses perpendicular vertical and horizontal lines to connect data points and shades the area under these lines. If a point's value is
null, the series draws a gap.
null point values result in gaps.
undefined values are ignored. Multiple 0 values may look like a gap, but if series points are visible, you can see them in this gap. If you want to remove gaps caused by
null values, enable the ignoreEmptyPoints property.