[BUG]: Trigger crashes with "TypeError: source.toLowerCase is not a function"

[GeorgSchmitz]

Describe the bug
Thank you very much for providing this node. Unfortunately I'm running into a problem where I cannot find a solution by myself. I use an ics calendar file from my local waste disposal company in order to remind me to move the bins to the street.
I'm using version 2.2.5 of your node running on a raspberry "bookworm" with node red running in version 3.1.9.
The same function works on my laptop using the same versions but running ArchLinux.
I have no idea how to catch the problem in order to solve it.

To Reproduce
Steps to reproduce the behavior:

1. input
   Use the "Abfallkalender" from www.schoenmackers.de select "Parkstraße", select "Hausnummer 2", tick the boxes "Bioabfall", "Leichtverpackungen", "Papier" and "Restabfall".
2. config
   I selected ical, gave it a name and placed the path to the file. The file is chmod 777 (for testing)
3. ouput
   TypeError: source.toLowerCase is not a function
   or when I start node red with the command: "DEBUG=kaldender-events* node-red"
   [error] [ical-events:Leichtverpackungen] TypeError: source.toLowerCase is not a function
   This fault message also applies for the other categories of rubbish bins.
4. See error

Expected behavior
When I use the trigger node, it shouldn't output fault messages

Screenshots

Additional context
I guess the fault is somehow caused by myself. But copying the complete node to a different machine does do the trick. It works out of the box with the same calendar file. I have no idea how to start solving the problem by myself and would be happy to get some support.

Thank you very much in advance!
Georg