ls-files: fix black space in error message

ce74de9(ls-files: introduce "--format" option) miss
a space between two words incorrectly, it leads to
wrong i10n messages. So fix it by adding a space at
the end of the error message.

Signed-off-by: ZheNing Hu <adlternative@gmail.com>
Signed-off-by: Junio C Hamano <gitster@pobox.com>

builtin/ls-files.c

@@ -257,7 +257,7 @@ static size_t expand_show_index(struct strbuf *sb, const char *start,
 
 	end = strchr(start + 1, ')');
 	if (!end)
-		die(_("bad ls-files format: element '%s'"
+		die(_("bad ls-files format: element '%s' "
 		      "does not end in ')'"), start);
 
 	len = end - start + 1;