layout.cell.attachUrl dock(), undock() Cannot set property 'onload' of null

Suite and Optimus Suite 5
#1

Use attachurl, undock () has no problem, but dock () throws an error.

How do you solve it?

error

#2

Please, try to call the dock() from the onContentLoaded event:
https://docs.dhtmlx.com/layout__attach_urls.html#usingoncontentloadedevent
If the problem still occurs for you please, provide a complete demo or a demo link, where the problem can be reconstructed locally.