Base path in admin menu cause error to non admin users.

Hi @NikolaAt, Is this patch really needed ? I have tested Admin Toolbar with your given Steps. But I am unable to replicate the issue. Its working fine for me. Can you please provide more explanation on it.

Hi, I also tried to reproduce the error and was unable to.
I created a custom link using the UI and there were no errors. Using version 3.4.2.

Its strange. If you say so, there is a chance the issue to be reproducible in combination with something else.
But in general I don't think its a bad idea make a validation, before we use something. Which is the patch that I made.