Steps:
1. Build and Run attached project ("WebRequestException.zip")

Expected: Build runs, a response from the server ("done! 200") is received and shown in the browser's console.
Actual: an unhandled exception appears, Build crashes.

Reproduced with: 2018.2.0a2, 2018.2.10f1, 2018.3.0b4, 2019.1.0a3.
Not reproduced with: 2017.4.12f1, 2018.1.9f2, 2018.2.0a1.

Note:
-if Scripting Runtime Version is .NET 3.5 Equivalent, the exception does not appear;
-if Enable Exceptions is set to any other than "None", the exception does not appear;
-no exception in Editor.