Tooltip not disappearing on null values

[rozxter1]

Description

Tooltip is not hidden over null values in single series line chart. might be because of tooltip.shared:false, setting this to true - shows empty tooltip

 tooltip: {
      shared: false,
  }

Steps to Reproduce

1. Move cursor to areas where null values - tooltip will be displayed over last point
2. Move cursor outside of chart from left or right side and enter in opposite side - tooltip will be displayed where it was last seen

Expected Behavior

Hide tooltip if there is null value. Dont show last tooltip on mouse enter into chart on empty area

Actual Behavior

Tooltip is displayed wrong and not dissapearing when needed and appearing when not needed

Screenshots

Reproduction Link

https://codepen.io/tzioo/pen/RwXYPeG