fix: test variables before returning

Signed-off-by: SebastianKrupinski <krupinskis05@gmail.com>

apps/dav/lib/CalDAV/EventReaderRRule.php

@@ -57,31 +57,31 @@ public function concludesOn(): DateTime | null {
 	}
 
 	public function daysOfWeek(): array {
-		return $this->byDay;
+		return is_array($this->byDay) ? $this->byDay : [];
 	}
 
 	public function daysOfMonth(): array {
-		return $this->byMonthDay;
+		return is_array($this->byMonthDay) ? $this->byMonthDay : [];
 	}
 
 	public function daysOfYear(): array {
-		return $this->byYearDay;
+		return is_array($this->byYearDay) ? $this->byYearDay : [];
 	}
 
 	public function weeksOfYear(): array {
-		return $this->byWeekNo;
+		return is_array($this->byWeekNo) ? $this->byWeekNo : [];
 	}
 
 	public function monthsOfYear(): array {
-		return $this->byMonth;
+		return is_array($this->byMonth) ? $this->byMonth : [];
 	}
 
 	public function isRelative(): bool {
 		return isset($this->bySetPos);
 	}
 
 	public function relativePosition(): array {
-		return $this->bySetPos;
+		return is_array($this->bySetPos) ? $this->bySetPos : [];
 	}
 
 }