Protect against null run process customizer

See 0ee277b8c3
See gh-32607

spring-boot-project/spring-boot-tools/spring-boot-maven-plugin/src/main/java/org/springframework/boot/maven/JavaProcessExecutor.java

@@ -65,7 +65,9 @@ class JavaProcessExecutor {
 	int run(File workingDirectory, List<String> args, Map<String, String> environmentVariables)
 			throws MojoExecutionException {
 		RunProcess runProcess = new RunProcess(workingDirectory, getJavaExecutable());
-		this.runProcessCustomizer.accept(runProcess);
+		if (this.runProcessCustomizer != null) {
+			this.runProcessCustomizer.accept(runProcess);
+		}
 		try {
 			int exitCode = runProcess.run(true, args, environmentVariables);
 			if (!hasTerminatedSuccessfully(exitCode)) {