TypeError: t.get is not a function

**Describe the bug**

I converted by "body" element type from "markdown" to "code" and made no other changes.

I switched back from code to markdown and it fixed.

My body is written in html which is awkward using the markdown editor

**To Reproduce**

convert a widget from `markdown` to `code`

**Expected behavior**

I should see the html / code editor

**Screenshots**

**Applicable Versions:**
- Netlify CMS version: `netlify-cms@2.10.60`
- Git provider: `git-gateway`
- Browser version: `Mozilla/5.0 (Windows NT 10.0; Win64; x64) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/85.0.4183.102 Safari/537.36`

**CMS configuration**
```
publish_mode: simple
slug:
encoding: unicode
clean_accents: false
sanitize_replacement: "-"
backend:
name: git-gateway
branch: master
media_folder: assets
collections:
- sortable_fields:
- commit_date
- title
- date
- commit_author
- description
view_filters: []
meta: {}
delete: false
name: post
slug: "{{year}}-{{month}}-{{day}}-{{slug}}"
folder: _posts
publish: true
label: Post
fields:
- label: layout
name: layout
widget: hidden
default: post
- label: Title
name: title
widget: string
- label: Description
name: description
widget: string
required: false
- label: Publish Date
name: date
widget: date
default: "{{year}}-{{month}}-{{day}}"
- label: type
name: type
widget: hidden
default: post
- label: published
name: published
widget: hidden
default: "true"
- label: status
name: status
widget: hidden
default: publish
- label: Upload Image
name: thumbnail
widget: image
- label: Categories
name: categories
widget: list
allow_add: true
- label: Tags
name: tags
widget: list
allow_add: true
- label: Body
name: body
widget: code
create: true
sort: date:asc
extension: html
public_folder: /assets

```

**Additional context**