Reproduction steps:
1. Open the user's attached project and Scenes/SampleScene scene
2. In the Hierarchy window, select Server GameObject
3. In the Inspector window, disable PadPacketsOfBadLength
4. Enter the Play mode

Expected result: Writing bytes to the driver when packet's size is 1386, 1387 or 1388 succeeds and Unity doesn't crash
Actual result: Writing bytes to the driver when packet's size is 1386, 1387 or 1388 fails and Unity crashes

Reproducible with: (0.6.0-preview.7) 2020.2.4f1, 2021.1.0b7, 2021.2.0a5
Could not test with: 2018.4.32f1 (Unity Transport is not available), 2019.4.20f1 (could not downgrade Unity Transport package)

Notes:
1. Errors from the Editor.log:
"Error whilst writing bytes to driver (size=1386) - see below exception.",
"System.InvalidOperationException: System.NullReferenceException: Object reference not set to an instance of an object
This Exception was thrown from a function compiled with Burst, which has limited exception support.
Stacktrace truncated - please add `Debug = true` to BurstCompile.
0x00007ff6eb1caffd (Unity) burst_signal_handler
0x00007ff9f64a83dc (ntdll) RtlDeleteAce
0x00007ff9f647b406 (ntdll) RtlRaiseException
0x00007ff9f64cfe3e (ntdll) KiUserExceptionDispatcher
0x00007ff9ab1a12b0 (a54e8b170e4c6a40f23838b19e1d51b) burst.initialize0"