CAMEL-24651: Fix NPE in ExceptionHelper.stackTraceToString() when exception is null

core/camel-core/src/test/java/org/apache/camel/language/simple/SimpleTest.java

@@ -641,6 +641,14 @@ public void testExceptionStacktrace() {
         assertTrue(out.contains("at org.apache.camel.language."));
     }
 
+    @Test
+    public void testExceptionStacktraceNoException() {
+        // CAMEL-24651
+        String out = context.resolveLanguage("simple").createExpression("${exception.stacktrace}").evaluate(exchange,
+                String.class);
+        assertNull(out);
+    }
+
     @Test
     public void testException() {
         exchange.setException(new IllegalArgumentException("Just testing"));

core/camel-support/src/main/java/org/apache/camel/support/ExceptionHelper.java

@@ -33,9 +33,12 @@ private ExceptionHelper() {
      * Dumps the stack trace from the given exception to a String
      *
      * @param  e the exception to print the stack trace
-     * @return   A string instance with the stack trace for the given exception
+     * @return   A string instance with the stack trace for the given exception, or null if the exception is null
      */
     public static String stackTraceToString(Throwable e) {
+        if (e == null) {
+            return null;
+        }
         final StringWriter writer = new StringWriter();
         final PrintWriter printWriter = new PrintWriter(writer, true);
         e.printStackTrace(printWriter);