[BUG] Transforms create transforms crashes when mapping is an object

[annie3431]

Describe the bug
The step 2 of create transform page crashes when attempting to show a column if mapping with object type.

To Reproduce
Steps to reproduce the behavior:

1. Install sample flight data.
2. Go to index management/transforms page
3. Click "Create transform"
4. Define fields on step 1, select sample data flights as source index, and go to step 2.
5. On the define transforms table click on "show column" and select "DestLocation", the page should crash.

Expected behavior
The mapping should be parsed to string showing {"lat: number, "lon: number}"

Screenshots

Desktop (please complete the following information):

• OS: [e.g. iOS]
• Browser [e.g. chrome, safari]
• Version [e.g. 22]

Additional context
Add any other context about the problem here.