To reproduce:

1.Download and open attached project.
2.Go to "BadQualityOfInternalTesting" folder and open "Test" scene.
3.Expand "Canvas" gameObject.
4.Expand "GameObject" gameObject.
5.Select "Panel" gameObject
6.Check the Console window.

Expected result: No messages are thrown in Console.
Actual result: "Look rotation viewing vector is zero" message is constantly shown in the console.

Reproduced with: 5.6.0b6, 5.5.1p2.

Notes: Could not reproduce on earlier versions because of backport issues. Can not reproduce it from scratch. Bug only occurs when "GameObject" gameObject has it's Rect transform's Width and Height properties are set to 0.