fix: NullAway warnings

Signed-off-by: Piotr P. Karwasz <piotr@github.copernik.eu>

Author: ppkarwasz

core/spring-boot/src/main/java/org/springframework/boot/logging/log4j2/Log4J2RuntimeHints.java

@@ -16,6 +16,8 @@
 
 package org.springframework.boot.logging.log4j2;
 
+import org.jspecify.annotations.Nullable;
+
 import org.springframework.aot.hint.RuntimeHints;
 import org.springframework.aot.hint.RuntimeHintsRegistrar;
 import org.springframework.util.ClassUtils;
@@ -28,7 +30,7 @@
 class Log4J2RuntimeHints implements RuntimeHintsRegistrar {
 
 	@Override
-	public void registerHints(RuntimeHints hints, ClassLoader classLoader) {
+	public void registerHints(RuntimeHints hints, @Nullable ClassLoader classLoader) {
 		if (!ClassUtils.isPresent(Log4J2LoggingSystem.Factory.LOG4J_CORE_CONTEXT_FACTORY, classLoader)) {
 			return;
 		}
@@ -58,7 +60,7 @@ public void registerHints(RuntimeHints hints, ClassLoader classLoader) {
 	 * @param classLoader the class loader to use for type resolution
 	 * @param typeName the name of the type to register
 	 */
-	private void registerTypeForReachability(RuntimeHints hints, ClassLoader classLoader, String typeName) {
+	private void registerTypeForReachability(RuntimeHints hints, @Nullable ClassLoader classLoader, String typeName) {
 		hints.reflection().registerTypeIfPresent(classLoader, typeName);
 	}