Selecting 'Create branch' after searching for a branch, will show two overlapping dialogs to create a branch

Summary

Selecting 'Create branch' after searching for a branch, will show two overlapping dialogs to create a branch

Environment

Chrome, latest version 60.0.3112.78

Steps to Reproduce

1. Open a repository
2. Go to Branches
3. Enter any term in the search box at the top right of the page
4. Then select 'Create branch'

Expected Results

The 'Create branch' dialog will show normally:

Actual Results

Two dialogs show up like follows: