To reproduce:

1. Open attached project
2. Make sure that Game tab is open
3. Select 2DSprite game object in hierarchy
4. Set Sprite property of the Sprite Renderer to transparentImage
5. Observe console

Expected: no errors are thrown when using an empty sprite
Actual: "Dynamic batching: index buffer source is NULL (first IB byte 0 count 0 first vertex 0 offset 0)" error is thrown when using an empty sprite

Reproduced in 5.6.0f1, 5.6.0f2, 5.6.0f3. Could not reproduce in 5.5.2p4 and 2017.1.0a6. Regression introduced in 5.6.0f1.