[EventPipe] Null passed as an event argument causes crash

Test: coreclr\tests\src\tracing\eventsource\eventsourcetrace\EventSourceTrace.cs Line 23: this.WriteEvent(1, x, y, z, null);

F:\TempRepo\coreclr>bin\tests\Windows_NT.x64.Debug\tracing\eventsource\eventsourcetrace\eventsourcetrace\eventsourcetrace.cmd
BEGIN EXECUTION
 "F:\TempRepo\coreclr\bin\tests\Windows_NT.x64.Debug\Tests\Core_Root\corerun.exe" eventsourcetrace.exe
        Start: Enable tracing.
        End: Enable tracing.

        Start: Messaging.

Unhandled Exception: System.Diagnostics.Tracing.EventSourceException: Null passed as a event argument.
   at System.Diagnostics.Tracing.EventSource.ThrowEventSourceException(String eventName, Exception innerEx)
   at System.Diagnostics.Tracing.EventSource.WriteEventVarargs(Int32 eventId, Guid* childActivityID, Object[] args)
   at System.Diagnostics.Tracing.EventSource.WriteEvent(Int32 eventId, Object[] args)
   at Tracing.Tests.SimpleEventSource.MathResult(Int32 x, Int32 y, Int32 z, String formula) in F:\TempRepo\coreclr\tests\src\tracing\eventsource\eventsourcetrace\EventSourceTrace.cs:line 23
   at Tracing.Tests.EventSourceTrace.Main(String[] args) in F:\TempRepo\coreclr\tests\src\tracing\eventsource\eventsourcetrace\EventSourceTrace.cs:line 75
Expected: 100
Actual: 255
END EXECUTION - FAILED
FAILED