Try to move Fields with Conditions not working

### Are you submitting a **bug report** or a **feature request**?

Bug report

### What is the current behavior?

When I try to Drag and Drop group of Fields with conditions to be displayed or not in a FieldArray, there is an error happening: "Cannot read property 'active' of undefined"

If you try to reproduce it from the sandbox linked below:

1. Create several customers
2. Enter on one of them "test" to validate the condition to display the lastName
3. Try to Drag and Drop a customer with the handler on the left "::"
4. The error come here 🔴

### What is the expected behavior?

The expected behavior is to be able to move Fields that have Conditions Fields inside

### Sandbox Link

[](https://codesandbox.io/s/ooowlmx42y)

Start with the linked CodeSandbox and reproduce the error by creating customers, entering "test" to conditionally display lastName, then dragging a customer with the "::" handler. Trace the FieldArray drag-and-drop path around the "Cannot read property 'active' of undefined" error; done means conditionally rendered fields can be moved without an error.

Written by the indexing model from the issue text.