Protect against empty OS string in Docker Image

Update `Image` to protect against `os` being `null` or and empty
String.

Fixes gh-45152

Author: philwebb

spring-boot-project/spring-boot-actuator-autoconfigure/src/test/java/org/springframework/boot/actuate/autoconfigure/security/servlet/ManagementWebSecurityAutoConfigurationTests.java

@@ -178,6 +178,7 @@ private HttpStatus getResponseStatus(AssertableWebApplicationContext context, St
 	static class CustomSecurityConfiguration {
 
 		@Bean
+		@SuppressWarnings("removal")
 		SecurityFilterChain securityFilterChain(HttpSecurity http) throws Exception {
 			http.authorizeHttpRequests((requests) -> {
 				requests.requestMatchers(new AntPathRequestMatcher("/foo")).permitAll();
@@ -207,6 +208,7 @@ static class TestRemoteDevToolsSecurityFilterChainConfig extends TestSecurityFil
 
 		@Bean
 		@Order(SecurityProperties.BASIC_AUTH_ORDER - 1)
+		@SuppressWarnings("removal")
 		SecurityFilterChain testRemoteDevToolsSecurityFilterChain(HttpSecurity http) throws Exception {
 			http.securityMatcher(new AntPathRequestMatcher("/**"));
 			http.authorizeHttpRequests((requests) -> requests.anyRequest().anonymous());

spring-boot-project/spring-boot-tools/spring-boot-buildpack-platform/src/main/java/org/springframework/boot/buildpack/platform/docker/type/Image.java

@@ -26,6 +26,7 @@
 import com.fasterxml.jackson.databind.JsonNode;
 
 import org.springframework.boot.buildpack.platform.json.MappedObject;
+import org.springframework.util.StringUtils;
 
 /**
  * Image details as returned from {@code Docker inspect}.
@@ -90,7 +91,7 @@ public List<LayerId> getLayers() {
 	 * @return the image OS
 	 */
 	public String getOs() {
-		return (this.os != null) ? this.os : "linux";
+		return (!StringUtils.hasText(this.os)) ? this.os : "linux";
 	}
 
 	/**