Steps to reproduce:
Preconditions:

• Use Firefox browser
• Pie chart widget with at least 2 data sets is added to the dashboard

1. Open dashboard with pie chart widget
2. Move to mouse pointer to data displayed in the pie chart widget
3. See the browser's console

Result:
Error: "Uncaught TypeError: e.toElement is undefined" is appearing in the console

See screenshot:

Expected:
No errors should appear in the console