Fix NullPointerException in Exception Replay (#12429)

Fix NullPointerException in Exception Replay

For FastThrow, getStackTrace can return null instead of empty
StackTraceElement array

call only once getStackTrace

fix possible NPE from chained exceptions

Co-authored-by: devflow.devflow-routing-intake <devflow.devflow-routing-intake@kubernetes.us1.ddbuild.io>

Author: jpbempel

dd-java-agent/agent-debugger/src/main/java/com/datadog/debugger/exception/AbstractExceptionDebugger.java

@@ -93,9 +93,12 @@ public void handleException(Throwable t, AgentSpan span) {
       Throwable throwable;
       int chainedExceptionIdx = 0;
       while ((throwable = chainedExceptions.pollFirst()) != null) {
+        StackTraceElement[] stackTrace = throwable.getStackTrace();
+        if (stackTrace == null || stackTrace.length == 0) {
+          continue;
+        }
         ExceptionProbeManager.CreationResult creationResult =
-            exceptionProbeManager.createProbesForException(
-                throwable.getStackTrace(), chainedExceptionIdx);
+            exceptionProbeManager.createProbesForException(stackTrace, chainedExceptionIdx);
         if (creationResult.probesCreated > 0) {
           if (!applyConfigAsync) {
             applyExceptionConfiguration(fingerprint);

dd-java-agent/agent-debugger/src/main/java/com/datadog/debugger/exception/DefaultExceptionDebugger.java

@@ -54,7 +54,8 @@ protected boolean shouldHandleException(Throwable t, AgentSpan span) {
     }
     // do not handle exception with no stacktrace. cannot capture anything for it.
     // includes also FastThrow ones
-    if (t.getStackTrace().length == 0) {
+    StackTraceElement[] stackTrace = t.getStackTrace();
+    if (stackTrace == null || stackTrace.length == 0) {
       return false;
     }
     return circuitBreaker.trip();