You can ignore the entries in system.log for this issue. They are not relevant.
It seems like Magento thinks your base URL is undefined. I would troubleshoot several areas in the following order:
In Magento Admin, navigate to STORES > Settings > Configuration > GENERAL > Web, and open both Base URLs and Base URLs (Secure). Verify your values at each scope level (Website, Store, View).
In your directory structure, navigate to app/etc/env.php, and verify all your
In your database, query:
SELECT * FROM core_config_data WHERE path LIKE "%base%url%". Verify all of those values.
If all of these appear correct, then in your console from the root of your Magento installation, run the usual maintenance commands:
bin/magento cache:flush && bin/magento setup:upgrade && bin/magento setup:static-content:deploy -f
You may also want to manually delete the contents of
pub/static, being very carefully not to delete any .htaccess files. In that case, after deleting, run
bin/magento setup:static-content:deploy -f. See if this is any better.
The steps above are intended to locate every place that a base URL value could be wrong, including in the database and in cache, and correct it. I welcome anyone's comments if they're aware of a place I didn't think to check.
If all else fails, you may need to hunt through your code to find any extensions or modifications that may have screwed this up. For example, that's what another user had to do here:
I found the issue. In my case it was the module-theme/view/frontend/templates/pages/js/require_js.phtml, that was extendend and the var BASE_URL was deleted. That is why I have undefined in the url. I hope this helps others that have same issue.