Describe the bug
If you try to group the data in a Grid by a column that has a value of "null", the browser hangs, and an error appears in the console.

To Reproduce

1. Open this StackBlitz example
2. Group the Grid by "Unit Price" field

Expected behavior
The data should be grouped according to the values inside the UnitPrice column. A column with an empty header should appear for the group with a "null" value.

Screenshots

Workaround

Convert the "null" values to empty string with a code like this:
this.products.forEach((o) => { o.UnitPrice = o.UnitPrice === null ? '' : o.UnitPrice; });
Here is a modified example in which the above code is added to the getData method.