Sprint Field Rendered incorrectly during issue edit, see below:

Steps to replicate:

1. Create issue sub task
2. Move the sprint field in the screen
3. Noticed that the sprint field will affect the rendering of the field below it

Workaround

Move the sprint field above Epic field, as the sprint field is unable to be assigned to an Epic. Result as below:

Note: It does not affects the parent task, as parent task has the selection of sprint which rendered correctly.

Tested on:
Firefox 31.0 Chrome 36.0 Safari 7.0.5