fix(dict): work around bash-4.2 array nounset

Author: akinomyoga

completions/dict

@@ -42,11 +42,11 @@ _comp_cmd_dict()
     # shellcheck disable=SC2254
     case $prev in
         --database | -info | -${noargopts}[di])
-            _comp_compgen_split -- "$(_dictdata "${dict_options[@]}" -D)"
+            _comp_compgen_split -- "$(_dictdata ${dict_options[@]+"${dict_options[@]}"} -D)"
             return
             ;;
         --strategy | -${noargopts}s)
-            _comp_compgen_split -- "$(_dictdata "${dict_options[@]}" -S)"
+            _comp_compgen_split -- "$(_dictdata ${dict_options[@]+"${dict_options[@]}"} -S)"
             return
             ;;
     esac