Uncaught TypeError: Cannot read property 'value' of undefined

A custom `` field in an InsertModal throws an error. How to manage `select`s in the plugin?

A field:
```

Status code

CONFIRMED
NOT_CONFIRMED

```

An error thrown by the plugin:

```
InsertModalBody.js:51 Uncaught TypeError: Cannot read property 'value' of undefined
at InsertModalBody. (InsertModalBody.js:51)
at Array.forEach ()
at InsertModalBody.getFieldValue (InsertModalBody.js:41)
at InsertModal.__handleSave__REACT_HOT_LOADER__ (InsertModal.js:63)
at InsertModal._this.handleSave (InsertModal.js:54)
at InsertModalFooter.__handleSaveBtnClick__REACT_HOT_LOADER__ (InsertModalFooter.js:68)
at InsertModalFooter._this.handleSaveBtnClick (InsertModalFooter.js:46)
at Object.ReactErrorUtils.invokeGuardedCallback (ReactErrorUtils.js:69)
at executeDispatch (EventPluginUtils.js:85)
at Object.executeDispatchesInOrder (EventPluginUtils.js:105)
```