Thanks for reporting!

I can replicate this under the Folders node, will be fixed as https://www.ventismedia.com/mantis/view.php?id=18536 in 2517+

Please capture this in a debug log (step 4b) and attach the log to a Support Ticket: https://www.mediamonkey.com/forum/viewtopic.php?f=30&t=86643

This will help a developer analyze why this happens in your setup.

OK. Updated to 2516. Error persists.
Screenshots:
1. https://drive.google.com/file/d/1l8SBX9oBImH8pgOULMIcgie_Hn24xAmZ/view?usp=sharing
2. https://drive.google.com/file/d/1g9LlNHxPH1q3oIYKaXFj5SvNrsvKme8E/view?usp=sharing

That's an old beta build, please update to the latest build which is 2516: https://www.mediamonkey.com/forum/viewtopic.php?f=30&t=86639

You can add screenshots as described at: https://www.mediamonkey.com/forum/viewtopic.php?f=1&t=97733

Build is 5.0.2.2507
I was hoping there was a way to post a jpg image of the error window here since it's a bit of a code dump.
However, the first line in it says: "Application throw an exception *Cannot read property 'dataSource' of undefined*
and then a few dozen lines of message and code follow.

What do the error message say and which Build (Help > About) of MediaMonkey 5 are you using?

Search returned what looked like the same problem and tagged as fixed. I still have a problem.
Selecting an Album and getting [b]List [/b]display, if I try to use the [b]Manage Views[/b] option under [b]Customize [/b]in the [b]Views[/b] dropdown (beside the List symbol, top right corn of the List display), I get an error popup. Selecting [b]Continue [/b]results in a second error popup and selecting [b]Continue[/b] on it finally gets me back to where I started.