Copy file button is duplicated when navigating back

[kidonng]

Steps to reproduce:

1. Open a file with "Copy file" button, for example https://github.com/EnixCoda/Gitako/blob/develop/Makefile
2. Click a PJAXed page, for example "History"
3. Navigate back
4. Notice the duplicate button

[EnixCoda]

Thank you!

[EnixCoda]

Fixed, will be included in the next release, v2.8.