Added missing status case where a tracked file has both staged and unstaged changes.

Two of the git prompt status flags, `ZSH_THEME_GIT_PROMPT_ADDED` and `ZSH_THEME_GIT_PROMPT_MODIFIED`, don't get added to the status prompt in the case where a tracked file has both staged and unstaged changes. When the theme doesn't use the dirty/clean flags, it can appear as if the repo is pristine.