Fix potential NPE in ApiCallAttemptTimeoutTrackingStage (#6332)

* fix potential NullPointerException in ApiCallAttemptTimeoutTrackingStage when exception is thrown before the tracker can be set in the context

* changelog

* updated changelog description

Author: L-Applin

.changes/next-release/bugfix-AWSSDKforJavav2-71c9a16.json

@@ -0,0 +1,6 @@
+{
+    "type": "bugfix",
+    "category": "AWS SDK for Java v2",
+    "contributor": "",
+    "description": "Fix a potential NullPointerException that may be thrown when API call timeout is configured"
+}

core/sdk-core/src/main/java/software/amazon/awssdk/core/internal/http/pipeline/stages/ApiCallAttemptTimeoutTrackingStage.java

@@ -111,7 +111,8 @@ private Exception translatePipelineException(RequestExecutionContext context, Ex
         // but before we called timeoutTracker.cancel(). Note that if hasExecuted() returns true, its guaranteed that
         // the timeout tracker has set the interrupt flag, and if it returns false, it guarantees that it did not and
         // will never set the interrupt flag.
-        if (context.apiCallAttemptTimeoutTracker().hasExecuted()) {
+        TimeoutTracker timeoutTracker = context.apiCallAttemptTimeoutTracker();
+        if (timeoutTracker != null && timeoutTracker.hasExecuted()) {
             // Clear the interrupt flag. Since we already have an exception from the call, which may contain information
             // that's useful to the caller, just return that instead of an ApiCallTimeoutException.
             Thread.interrupted();
@@ -136,7 +137,8 @@ private RuntimeException handleInterruptedException(RequestExecutionContext cont
                                                                         "Failed to close the response stream",
                                                                         r::close));
         }
-        if (context.apiCallAttemptTimeoutTracker().hasExecuted()) {
+        TimeoutTracker timeoutTracker = context.apiCallAttemptTimeoutTracker();
+        if (timeoutTracker != null && timeoutTracker.hasExecuted()) {
             // Clear the interrupt status
             Thread.interrupted();
             return generateApiCallAttemptTimeoutException(context);