magento2 – Containerized Magento 2 resulting in `Expecting a string, got NULL` error when trying to adjust URLs

When running Magento 2 in a multi-container docker compose setup, I’m receiving the following error:

1 exception(s):
Exception #0 (LaminasUriExceptionInvalidArgumentException): Expecting a string, got NULL

Exception #0 (LaminasUriExceptionInvalidArgumentException): Expecting a string, got NULL
<pre>#1 LaminasUriUri->parse(NULL) called at (vendor/magento/module-backend/App/Area/FrontNameResolver.php:140)
#2 MagentoBackendAppAreaFrontNameResolver->getHostWithPort(NULL) called at (vendor/magento/module-backend/App/Area/FrontNameResolver.php:129)
#3 MagentoBackendAppAreaFrontNameResolver->isHostBackend() called at (vendor/magento/module-backend/App/Area/FrontNameResolver.php:106)
#4 MagentoBackendAppAreaFrontNameResolver->getFrontName(true) called at (vendor/magento/framework/App/AreaList.php:76)
#5 MagentoFrameworkAppAreaList->getCodeByFrontName('home') called at (vendor/magento/framework/App/Http.php:111)
#6 MagentoFrameworkAppHttp->launch() called at (vendor/magento/framework/Interception/Interceptor.php:58)
#7 MagentoFrameworkAppHttpInterceptor->___callParent('launch', array()) called at (vendor/magento/framework/Interception/Interceptor.php:138)
#8 MagentoFrameworkAppHttpInterceptor->MagentoFrameworkInterception{closure}() called at (vendor/magento/framework/Interception/Interceptor.php:153)
#9 MagentoFrameworkAppHttpInterceptor->___callPlugins('launch', array(), array(array('Vaimo_RuntimeFla...', 'Vaimo_AjaxBlocks'))) called at (generated/code/Magento/Framework/App/Http/Interceptor.php:26)
#10 MagentoFrameworkAppHttpInterceptor->launch() called at (vendor/magento/framework/App/Bootstrap.php:261)
#11 MagentoFrameworkAppBootstrap->run(&MagentoFrameworkAppHttpInterceptor#0000000024ab3be90000000018e5fcf0#) called at (pub/index.php:40)
</pre>

I’m using a customized admin url and have modified the other urls as illustrated with the data from this query:

select * from core_config_data WHERE ( path LIKE '%admin/%url%') OR ( path LIKE 'web/%/%url%');

With the results being:

+-----------+---------+----------+---------------------------------------------------+----+-----------+---------+----------+---------------------------------------------------+-------------------------------------+---------------------+
| config_id | scope   | scope_id | path                                              | value                               | updated_at          |
+-----------+---------+----------+---------------------------------------------------+-------------------------------------+---------------------+
|         8 | default |        0 | web/unsecure/base_url                             | http://app.myURL.test            | 2021-06-08 20:24:18 |
|        11 | default |        0 | web/secure/base_url                               | https://app.myURL.test           | 2021-06-08 20:24:18 |
|       452 | default |        0 | web/canada_external_stores_config/canada_caen_url | https://myURL.ca/en/home/        | 2020-01-28 12:11:54 |
|       458 | default |        0 | web/canada_external_stores_config/canada_cafr_url | https://myURL.ca/fr/home/        | 2020-01-28 12:11:54 |
|       461 | default |        0 | web/unsecure/base_link_url                        | https://app.myURL.test           | 2021-06-08 20:24:18 |
|       464 | default |        0 | web/unsecure/base_static_url                      | NULL                             | 2020-01-28 12:11:54 |
|       467 | default |        0 | web/unsecure/base_media_url                       | NULL                             | 2020-01-28 12:11:54 |
|       470 | default |        0 | web/secure/base_link_url                          | https://app.myURL.test           | 2021-06-08 20:24:18 |
|       473 | default |        0 | web/secure/base_static_url                        | NULL                             | 2020-01-28 12:11:54 |
|       476 | default |        0 | web/secure/base_media_url                         | NULL                             | 2020-01-28 12:11:54 |
|      4451 | default |        0 | admin/url/use_custom                              | 1                                   | 2021-06-08 20:24:18 |
|      4454 | default |        0 | admin/url/use_custom_path                         | https://app.myURL.test/admin | 2021-06-08 20:24:20 |
+-----------+---------+----------+---------------------------------------------------+-------------------------------------+---------------------+

I’ve monkeyed with the base url in different configurations but no matter what I do, when I set the admin/url/use_custom_path and admin/url/use_custom I receive the above error. Can anyone point me to the next logical troubleshooting path?