Add some bug fixes for next_lesson and timetable builder

aleksis/apps/chronos/util/build.py

@@ -127,7 +127,7 @@ def build_timetable(
 
             for period in range(period_from, period_to + 1):
                 if period not in events_per_period:
-                    events_per_period[period] = [] if is_person else {}
+                    events_per_period[period] = {} if is_week else []
 
                 if is_week and weekday not in events_per_period[period]:
                     events_per_period[period][weekday] = []