Copying commit hash crashes Lazygit

I've tried to copy the hash from the reflog window via "CTRL + o" but got this message:

```
2020/12/14 14:21:13 An error occurred! Please create an issue at https://github.com/jesseduffield/lazygit/issues

*errors.errorString No clipboard utilities available. Please install xsel, xclip, wl-clipboard or Termux:API add-on for termux-clipboard-get/set.
github.com/jesseduffield/lazygit/main.go:133 (0xa09eb3)
runtime/proc.go:203 (0x43149e)
runtime/asm_amd64.s:1357 (0x45cec1)
```

Got fixed after installing xsel. I guess xsel or xclip should be a dependency.

**Environment:**
- OS: Ubuntu 20.04
- Lazygit Version : build date=2020-10-14, build source=debian, version=0.23.6, os=linux, arch=amd64