add missing @nullable

Author: SylvainJuge

instrumentation/jaxrs/jaxrs-3.0/jaxrs-3.0-annotations/javaagent/src/main/java/io/opentelemetry/javaagent/instrumentation/jaxrs/v3_0/DefaultRequestContextInstrumentation.java

@@ -108,7 +108,7 @@ public static AdviceScope createGenericSpan(
 
     @Advice.OnMethodExit(onThrowable = Throwable.class, suppress = Throwable.class)
     public static void stopSpan(
-        @Advice.Thrown Throwable throwable, @Advice.Enter AdviceScope adviceScope) {
+        @Advice.Thrown Throwable throwable, @Advice.Enter @Nullable AdviceScope adviceScope) {
 
       if (adviceScope != null) {
         adviceScope.exit(throwable);