Hi JaeHyeong,
Thanks for contacting Syncfusion Forums.
We are able to reproduce the issue at our end. We have considered it as a bug and logged report for the same. Thank you for taking time to report this issue "Script error occurs when the TreeGrid is rendered in splitter with the number of DataSource is 0 " and helping us improve our product. Fix for this issue will be included in our upcoming Volume 3 2020 SP1 release which is expected to be rolled out in 1st week of November 2020.
You can track the current status of your request, review the proposed resolution timeline and contact us for any further queries through this link,
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Kindly get back to us for further assistance.
Regards,
Padmavathy Kamalanathan