Deleting values from an array messes up subsequent keys/values in the array

[rosswintle]

Probably best demonstrated with a GIF:

Steps to reproduce:

1. Open the editor an empty serialized string
2. Add some key/value pairs (I've tried with both integer and string keys)
3. Delete a value from the middle of the array of values

Expected behaviour

Only the deleted key/value is removed - all other values are un-modified

Actual behaviour

The deleted key/value is removed. All subsequent key/values in the array are set to 0 => value