Steps to reproduce:

1. Create a Toaster project with release master
2. Build core-image-minimal
3. When the build is done, go the "new custom image" page, search for "core-image-minimal openembedded-core", and click the "customise" button for core-image-minimal
4. Give your custom image a name. Once your custom image is created, build it
5. Once the build is done, click on the image name to see the build dashboard

Outcome: in the 'Configuration' section of the build dashboard, you will see the following layers listed

Unidentified layer
meta-poky
meta-yocto-bsp
openembedded-core

That "unidentified layer" should be "toaster-custom-images" instead