Dropdown's don't retain their previous values

[kaidesu]

Describe the issue

Values set via dropdown don't retain their value on subsequent loads.

To reproduce

• Create a new matrix and set the type to "Page"
• Edit the matrix, and note that the values in dropdowns are just set to the first item (e.g. type is set to "Collection" and assigned fieldset is empty)

Screenshots

Version and browser

Version: Beta 6

Bug report checklist

• I have filled out as much information as I can
• I have detailed how the issue can be reproduced
• I have searched for existing issues and to the best of my knowledge this is not a duplicate