I'm glad [@]christopherjtaylor was able to resolve this in their case, but I'm not the admin for my organization and don't have access to our Google Admin Console (where Tasks is apparently set as disabled), so my Google Workspace account simply does not connect. I can't even work around the problem by using the secret iCal link that Google Calendar provides because, due to how events are represented internally, I sometimes end up with several copies of the same event in Vivaldi as a result. I imagine the necessary code change here would be as simple as a null guard, some other if statement, a try/catch block, or a new catch clause.
Info about my environment:
Vivaldi Version 7.3.3635.11 (Stable channel) (64-bit)
Windows 11 24H2 (26100.3915)
Intel Core i9-14900HX @ 2.20 GHz (x64-based)
NVIDIA GeForce RTX 4060 (Laptop)
32 GB RAM, ample M.2 SSD storage