[BUG] NullReferenceException in PayloadSenderV2 if APM is disabled

[th3ragex]

APM Agent version

1.28.5

Describe the bug

While debugging NullReferenceExceptions were observed in PayloadSenderV2.
The APM was disabled via: "ELASTIC_APM_ENABLED": "false",

apm-agent-dotnet/src/Elastic.Apm/Report/PayloadSenderV2.cs

Lines 184 to 185 in 9a99a2e

	_logger.Debug()
	?.Log("Queue reached max capacity - " + dbgEventKind + " will be discarded."

_logger was null, NRE was raised within Debug method.

Observed root causes:

1. Call of extension methods on null object
2. Execution of internal logic even though the object was not fully initialized

   apm-agent-dotnet/src/Elastic.Apm/Report/PayloadSenderV2.cs

   Lines 75 to 77 in 9a99a2e

   	{
   	if (!isEnabled)
   	return;

Expected behavior

1. Do not call Extension methods on null
2. Do not call EnqueueEventInternal if APM is disabled

[Mpdreamz]

Thanks for reporting this rather nasty bug @th3ragex 🙏 , we will be pushing a new release with a fix shortly.

[th3ragex]

@Mpdreamz Thank you for your fast and continuous support on this library! 🙏