Fix validation of process args metadata in Paketo system tests

Fixes gh-35894

spring-boot-system-tests/spring-boot-image-tests/src/systemTest/java/org/springframework/boot/image/assertions/ContainerConfigAssert.java

@@ -16,8 +16,10 @@
 
 package org.springframework.boot.image.assertions;
 
+import java.util.Collections;
 import java.util.List;
 import java.util.Map;
+import java.util.Objects;
 import java.util.function.Consumer;
 
 import com.github.dockerjava.api.model.ContainerConfig;
@@ -100,13 +102,12 @@ public class ContainerConfigAssert extends AbstractAssert<ContainerConfigAssert,
 			return this.actual.extractingJsonPathArrayValue("$.buildpacks[*].id");
 		}
 
-		@SuppressWarnings("unchecked")
 		public AbstractListAssert<?, List<? extends String>, String, ObjectAssert<String>> processOfType(String type) {
 			return this.actual.extractingJsonPathArrayValue("$.processes[?(@.type=='%s')]", type)
 				.singleElement()
 				.extracting("command", "args")
-				.flatExtracting((list) -> (List<String>) list);
-
+				.flatMap((list) -> (list != null) ? ((List<?>) list).stream().map(Objects::toString).toList()
+						: Collections.emptyList());
 		}
 
 	}