Steps to reproduce :

- create a canvas
- in the Canvas Scaler change the UI Scale Mode to Constant Physical Size
- delete the values in the Default Sprite DPI and notice the errors

*Note:
The errors pop up every time the field is empty, so backspacing, typing and backspacing should spam this error in the console.

Invalid AABB inAABB
UnityEngine.Canvas:SendWillRenderCanvases()

Regression from 5.1.