{*}Reproduction steps{*}:
# Create new project
# Create UI Document file (Project window > Create > UI Toolkit > UI Document)
# Open UI Document
# Drag in the "Dropdown" element
# Check the "Choices" field
# Save the document
# Check the "Choices" field again

{*}Expected result{*}: The "Choices" field is not changed

{*}Actual result{*}: "Choices" field gets filled with "System.Collections.Generic.List`1[System.String]"

{*}Note{*}: Also reproducible when unsetting the "Choices" field and undoing the unset