Avoid warning when inside of .git dir

We cannot detect untracked files when we are inside of
a .git directory.

functions/vcs.zsh

@@ -8,6 +8,8 @@
 
 set_default POWERLEVEL9K_VCS_SHOW_SUBMODULE_DIRTY false
 function +vi-git-untracked() {
+    [[ -z "${vcs_comm[gitdir]}" || "${vcs_comm[gitdir]}" == "." ]] && return
+
     if [[ "$POWERLEVEL9K_VCS_SHOW_SUBMODULE_DIRTY" == "true" && "$(command git submodule foreach --quiet --recursive 'command git ls-files --others --exclude-standard')" != "" ]]; then
         hook_com[unstaged]+=" $(print_icon 'VCS_UNTRACKED_ICON')"
         VCS_WORKDIR_HALF_DIRTY=true