Illustrator crashes when a spot name with 4-byte and Surrogate Pair characters is applied on Freeform gradient

Issue

When you use Japanese Illustrator build on a Japanese OS, Illustrator crashes if you perform the following task:

1. Create a new CMYK document.
2. Create a Spot color with a name that includes 4-byte or Surrogate Pair characters, and save it in the Swatches Panel.
3. Create a rectangle object and apply Freeform gradient on this object.
4. Double-click a color stop to modify its fill color.
5. Now, in the Swatches panel, select the color you saved in step 2.
6. Apply the selected color and close the Swatches panel. 
7. Click outside the artboard.

Observations

You may observe the following:

• Many new spot colors with no name start getting added to the Swatches panel. If you are using Windows OS, the loop stops when you click on the artboard. However, it does not stop for macOS. 
• If you now apply another spot color with a name that contains 4-byte or Surrogate Pair characters to another color spot, Illustrator crashes.
• This issue can be seen only with 4- byte characters and Surrogate pair characters. The two-byte characters work well.