Make the text for empty days configurable

The default is "--"; a single space makes the text invisible.

Signed-off-by: Lars Henriksen <LarsHenriksen@get2net.dk>
Signed-off-by: Lukas Fleischer <lfleischer@calcurse.org>

src/vars.c

@@ -127,6 +127,7 @@ void vars_init(void)
 	conf.event_separator = 1;
 	conf.day_separator = 1;
 	conf.empty_appt_line = 1;
+	strcpy(conf.empty_day, EMPTY_DAY_DEFAULT);
 	conf.confirm_quit = 1;
 	conf.confirm_delete = 1;
 	conf.auto_save = 1;