Test optional directories without sub-directories

Add an additional test to ensure that optional wildcard
directory patterns do not fail.

See gh-26677

spring-boot-project/spring-boot/src/test/java/org/springframework/boot/context/config/ConfigDataEnvironmentPostProcessorIntegrationTests.java

@@ -719,6 +719,12 @@ class ConfigDataEnvironmentPostProcessorIntegrationTests {
 						"Config data location 'file:src/test/resources/config/0-empty/*/' contains no subdirectories");
 	}
 
+	@Test
+	void runWhenOptionalWildcardLocationHasNoSubdirectories() {
+		assertThatNoException().isThrownBy(() -> this.application
+				.run("--spring.config.location=optional:file:src/test/resources/config/0-empty/*/"));
+	}
+
 	@Test
 	void runWhenHasMandatoryWildcardLocationThatDoesNotExist() {
 		assertThatExceptionOfType(ConfigDataLocationNotFoundException.class)