Sprite Material vanishes upon hitting Play

This afternoon I added another sprite to my 2D game and this time when I hit Play the sprite vanished. Turns out the Sprite Renderer > Material is being changed to None (even if I save the scene before hitting Play).

If I manually change the Material back to Sprite - Default then everything is back to normal and it works fine when I hit Play.

What's (especially) odd is that previously today dragging sprites into the game worked just fine -- I don't recall doing anything "weird" that made the problem crop up.

Jay

PS - Using 5.4.0b17 on Mac, and quitting and restarting Unity didn't fix the problem. Only manually resetting the Material fixes it.

 

Follow-Up:

It appears the problem is that the default Sprite Renderer > Material that's put in when I drag an image into the scene is Sprites/Default but the one that's in the Materials picker is Sprites-Default. So I think it's looking for the one with the slash and when it doesn't find that it just blanks out the field, requiring you to manually set it.

Just in case someone wants to fix that...

Jay