fix: array must be empty if it contains an undefined element

Co-authored-by: Vincent Hyvert <[email protected]>

Author: maelgangloff

src/models/Calendar/index.ts

@@ -35,7 +35,7 @@ END:VEVENT`
   }
 
   public toICalendar (dtstamp: Date = new Date(), name = 'Agenda Skolengo'): string {
-    const lessons = this.map(j => j.lessons).flat()
+    const lessons = [...this].map(j => j.lessons).flat()
     const calendarName = name ?? 'Agenda Skolengo'
     return `BEGIN:VCALENDAR
 VERSION:2.0

src/models/SchoolLife/index.ts

@@ -11,7 +11,7 @@ export class AbsenceFilesResponse extends Array<AbsenceFile> {
 
   public toCSV (): string {
     return 'created,type,status,start,end,reason,reason_label\n' +
-    this.map(file => {
+    [...this].map(file => {
       const {
         creationDateTime,
         absenceType,