highslide-software/highcharts.com — Issue #514: Avoid "is null or not an object" Exceptions on tooltipPoints in IE 8 
Author: r3to
Created: 2011-10-21 15:16:21+00:00
State: open

I changed
```if (series[j].visible && series[j].tooltipPoints.length) ```
on line 6431 to
```if (series[j].visible && series[j].tooltipPoints !== undefined)```
to avoid a long list of Exceptions on the console