fix(render): show message if not yet committed

[futsuuu]

When using a local plugin that has not yet been commited, the following error occurs when trying to view plugin information.

Error executing vim.schedule lua callback: ...local/share/nvim/lazy/lazy.nvim/lua/lazy/view/render.lua:502: attempt to index field 'commit' (a nil value)
stack traceback:
        ...local/share/nvim/lazy/lazy.nvim/lua/lazy/view/render.lua:502: in function 'details'
        ...local/share/nvim/lazy/lazy.nvim/lua/lazy/view/render.lua:422: in function 'plugin'
        ...local/share/nvim/lazy/lazy.nvim/lua/lazy/view/render.lua:239: in function 'section'
        ...local/share/nvim/lazy/lazy.nvim/lua/lazy/view/render.lua:71: in function 'update'
        .../.local/share/nvim/lazy/lazy.nvim/lua/lazy/view/init.lua:142: in function 'fn'
        ...tsuuu/.local/share/nvim/lazy/lazy.nvim/lua/lazy/util.lua:72: in function <...tsuuu/.local/share/nvim/lazy/lazy.nvim/lua/lazy/util.lua:71>

So make it show No commits yet if git.commit is nil.

[folke]

Maybe better to just not show the commit here in this case? So just drop the else part?

[futsuuu]

In my case, git.commit was nil but git.branch was not nil, so I thought it would be better to show the commit as well, just in case.
However, it is not always the case that git.commit does not become nil in other cases, so I should certainly drop the else part.