Cannot select mask layer only

[Keyless]

On the desktop version of Photo for Mac (High Sierra) I created a mask for an image layer. When I attempt to select the mask layer it also selects the parent image layer along with the child mask layer. I'm unable to select only the mask layer. As such, when I attempt to paint on the mask layer, it paints on the image layer, thereby ruining it. I imported the same project file into the iPad version of Photo, where it works just fine and I can select only the mask layer and thereby paint only on the mask layer without affecting the parent image layer. When I import the same file back into the desktop version, the issue persists. I also tried this with a different file and the problem is exactly the same. So the problem seems to be reproducible. 

[walt.farrell]

Did you try clicking on the thumbnail?

[Keyless]

3 hours ago, walt.farrell said:

Did you try clicking on the thumbnail?

That did it! Thank you. Not a bug!

[walt.farrell]

You're welcome.