pressed_date initialization

pressed_date inited in create function.

lv_objx/lv_calendar.c

@@ -97,7 +97,11 @@ lv_obj_t * lv_calendar_create(lv_obj_t * par, const lv_obj_t * copy)
     ext->showed_date.year = 2018;
     ext->showed_date.month = 1;
     ext->showed_date.day = 1;
-
+    
+    ext->pressed_date.year = 0;
+    ext->pressed_date.month = 0
+    ext->pressed_date.day = 0
+ 
     ext->highlighted_dates  = NULL;
     ext->highlighted_dates_num = 0;
     ext->day_names = NULL;