fix nil dereference

Author: firu11

pkg/core/core_events.go

@@ -277,7 +277,7 @@ func (c *Core) updateFollowingChildren(old, new *Event) (*Event, error) {
 	newEvent.Id = uuid.New()     // assign new id
 	newEvent.ParentId = uuid.Nil // not child anymore
 
-	if originalCount != 0 {
+	if originalCount != 0 && newEvent.Repeat != nil {
 		// shorten the repeat for the second half
 		_, elapsed := firstOccurrenceAtOrAfter(old.From, parent)
 		if elapsed <= 0 {

pkg/core/event.go

@@ -29,7 +29,7 @@ type Event struct {
 	Calendar    string      `json:"calendar,omitzero"`  // The name of the calendar the event belongs to.
 	Tag         string      `json:"tag,omitzero"`       // User-defined category or label.
 	ParentId    uuid.UUID   `json:"parent_id,omitzero"` // Specific for child events. It is uuid.Nil if the event is basic or parent.
-	Repeat      *Repetition `json:"repeat,omitzero"`    // nil if child
+	Repeat      *Repetition `json:"repeat,omitzero"`
 }
 
 // Repetition defines the recurrence rules for a Parent event.