Roundcube gives Internal Server Error when adding an event

Symptoms

When attempting to add an event to the RoundCube calendar, the following error is logged to the RoundCube error log:

PHP Fatal error:  Uncaught TypeError: count(): Argument #1 ($value) must be of type Countable|array, false given in /usr/local/cpanel/base/3rdparty/roundcube/plugins/libcalendaring/lib/libcalendaring_vcalendar.php:1450

Description

We've opened an internal case for our development team to investigate this further. For reference, the case number is CPANEL-47609. Follow this article to receive an email notification when a solution is published in the product. 

Workaround

Change line:

/usr/local/cpanel/base/3rdparty/roundcube/plugins/libcalendaring/lib/libcalendaring_vcalendar.php

From:

if (count($transitions) == 1) {

To:

if ( !empty($transitions) && count($transitions) == 1) {