sr.getResponseDataAsString().length() throwing exception because getResponseDataAsString() is null

[dlebsock]

HI!

This plugin has been very useful for propogating logs to my AI instance. There is one hiccup that I have run into, and that getResponseDataAsString() is returning null when there is no response returned. logResponseData is set to always but there are instances when a response is not returned..

jmeter-backend-azure/src/main/java/io/github/adrianmo/jmeter/backendlistener/azure/AzureBackendClient.java

Lines 247 to 254 in 37f2d84

	if (logResponseData == DataLoggingOption.Always ||
	(logResponseData == DataLoggingOption.OnFailure && !sr.isSuccessful())) {
	String responseData;
	if (sr.getResponseDataAsString().length() > MAX_DATA_LENGTH) {
	log.warn("Response data is too long, truncating it to {} characters", MAX_DATA_LENGTH);
	responseData = sr.getResponseDataAsString().substring(0, MAX_DATA_LENGTH) + "...[TRUNCATED]";
	} else {
	responseData = sr.getResponseDataAsString();

Here is a sample stack trace showcasing the issue:

2024-01-03 21:29:18,296 ERROR o.a.j.JMeter: Uncaught exception in thread Thread[Thread-4,5,main]
java.lang.NullPointerException: Cannot invoke "String.length()" because the return value of "org.apache.jmeter.samplers.SampleResult.getResponseDataAsString()" is null
at io.github.adrianmo.jmeter.backendlistener.azure.AzureBackendClient.trackRequest(AzureBackendClient.java:250) ~[jmeter.backendlistener.azure-0.2.9.jar:?]
at io.github.adrianmo.jmeter.backendlistener.azure.AzureBackendClient.handleSampleResults(AzureBackendClient.java:274) ~[jmeter.backendlistener.azure-0.2.9.jar:?]
at org.apache.jmeter.visualizers.backend.BackendListener.sendToListener(BackendListener.java:254) ~[ApacheJMeter_components.jar:5.5]
at org.apache.jmeter.visualizers.backend.BackendListener.access$600(BackendListener.java:50) ~[ApacheJMeter_components.jar:5.5]
at org.apache.jmeter.visualizers.backend.BackendListener$Worker.run(BackendListener.java:225) ~[ApacheJMeter_components.jar:5.5]

Thank you!