Error after upgrade

[geoff1210]

I just upgraded Netbox from v3.8.7 to v4.2.3 and I'm getting the following error when I try to get the application going:

Server Error
There was a problem with your request. Please contact an administrator.

The complete exception is provided below:

<class 'django.template.exceptions.TemplateSyntaxError'>

Invalid block tag on line 118: 'plugin_alerts', expected 'endblock'. Did you forget to register or load this tag?

Python version: 3.12.3
NetBox version: 4.2.3
Plugins: None installed

Could use some help diagnosing what is going wrong here - I am not sure the best course of action or why it's upset. To my knowledge, we've never utilized plugins.

[geoff1210]

I uh... resolved... this by going into the following template html file and deleting the reference to {% plugin_alerts object %}
/opt/netbox/netbox/templates/generic/object.html

I repeated the process in the following template html file deleting a reference to {% plugin_navbar %}
/opt/netbox/netbox/templates/base/layout.html

This does not feel like a permanent root-cause type solution to the problem at hand but my netbox is functioning again. Interested to know if I missed a step during the upgrade or what could be going on here.