To reproduce:

1. Download attached project "New Unity Project (2).zip" and open in Unity
2. Open "SampleScene" scene
3. Go to Edit > Preferences... and click External Tools
4. Delete Android JDK path
5. Click Edit > Build Settings
6. Hover mouse on and off Build Settings window

Expected results: There should be only one error or the same behavior as 2018.2 and 2018.3 have
Actual result: A lot of "UnityException" errors appears

Notes:
- This issue appears only on Windows platform
- On OSX no error is printed
- If you try to build the project, it should fail because there is no JDK path

Reproduced on Unity 2018.1.0b6 and 2018.1.5f1
Not reproduced on Unity 2017.4.5f1, 2018.1.0b5, 2018.2.0b9 and 2018.3.0a2
Regression on Unity 2018.1.0b6