Ensure default tab style is complete-word

Fixes a bug introduced by 7b1a81c.

scripts/.autocomplete.key-binding

@@ -11,8 +11,10 @@ zmodload -F zsh/parameter p:funcstack p:functions
       builtin zstyle ':autocomplete:shift-tab:*' insert-unambiguous yes
 
   local tab_style=
-  builtin zstyle -s :autocomplete:tab: widget-style tab_style ||
-      tab_style='complete-word'
+  if ! builtin zstyle -s :autocomplete:tab: widget-style tab_style; then
+    tab_style='complete-word'
+    builtin zstyle ':autocomplete:tab:*' widget-style $tab_style
+  fi
 
   if builtin zstyle -t :autocomplete:tab: fzf-completion &&
       [[ -v functions[fzf-completion] ]]; then
@@ -35,8 +37,10 @@ zmodload -F zsh/parameter p:funcstack p:functions
   fi
 
   local backtab_style=
-  builtin zstyle -s :autocomplete:shift-tab: widget-style backtab_style ||
-      backtab_style=${tab_style:/menu-complete/reverse-menu-complete}
+  if ! builtin zstyle -s :autocomplete:shift-tab: widget-style backtab_style; then
+    backtab_style=${tab_style:/menu-complete/reverse-menu-complete}
+    builtin zstyle ':autocomplete:shift-tab:*' widget-style $backtab_style
+  fi
 
   builtin bindkey -M emacs $terminfo[kcbt] $backtab_style
   builtin bindkey -M viins $terminfo[kcbt] $backtab_style