Steps to reproduce:
1. Open user-supplied project ("BugReport.zip")
2. Run Scene "SampleScene"

Expected: no error is thrown
Actual: error is thrown after a couple of seconds

Reproduced in: 2018.3.0a1, 2018.4.2f1, 2019.1.4f1, 2019.2.0b5, 2019.3.0a5
Not reproduced in: 2017.4.29f1

Note:
Full error:
Uncatchable thread exception: System.AggregateException: A Task's exception(s) were not observed either by Waiting on the Task or accessing its Exception property. As a result, the unobserved exception was rethrown by the finalizer thread. ---> System.ObjectDisposedException: Cannot access a disposed object.

Object name: 'MobileAuthenticatedStream'.

at System.Runtime.ExceptionServices.ExceptionDispatchInfo.Throw () [0x0000c] in <1f0c1ef1ad524c38bbc5536809c46b48>:0

at Mono.Net.Security.MobileAuthenticatedStream+<StartOperation>d__58.MoveNext () [0x001bf] in <c9226b2f33b7421e85bb391f94075e49>:0

--- End of inner exception stack trace ---

---> (Inner Exception #0) System.ObjectDisposedException: Cannot access a disposed object.

Object name: 'MobileAuthenticatedStream'.

at System.Runtime.ExceptionServices.ExceptionDispatchInfo.Throw () [0x0000c] in <1f0c1ef1ad524c38bbc5536809c46b48>:0

at Mono.Net.Security.MobileAuthenticatedStream+<StartOperation>d__58.MoveNext () [0x001bf] in <c9226b2f33b7421e85bb391f94075e49>:0 <---

UnityEngine.Debug:Log(Object)
Test:LastExceptionHandler(Exception, String) (at Assets/Test.cs:55)
Test:<Start>b__0_0(Object, UnobservedTaskExceptionEventArgs) (at Assets/Test.cs:15)
System.Threading.Tasks.TaskExceptionHolder:Finalize()