Fix NPE in SimpleDataSourceProperties when driver is null

- Prevent NullPointerException in SimpleDataSourceProperties by adding null check before calling getDriver().getClass().
- Fixes potential crash when driver is not explicitly configured.

Signed-off-by: chanbinme <gksmfcksqls@gmail.com>

Author: chanbinme

spring-boot-project/spring-boot/src/main/java/org/springframework/boot/jdbc/DataSourceBuilder.java

@@ -712,7 +712,8 @@ private static class SimpleDataSourceProperties extends MappedDataSourceProperti
 		@SuppressWarnings("unchecked")
 		SimpleDataSourceProperties() {
 			add(DataSourceProperty.URL, SimpleDriverDataSource::getUrl, SimpleDriverDataSource::setUrl);
-			add(DataSourceProperty.DRIVER_CLASS_NAME, Class.class, (dataSource) -> dataSource.getDriver().getClass(),
+			add(DataSourceProperty.DRIVER_CLASS_NAME, Class.class,
+					(dataSource) -> dataSource.getDriver() == null ? null : dataSource.getDriver().getClass(),
 					SimpleDriverDataSource::setDriverClass);
 			add(DataSourceProperty.USERNAME, SimpleDriverDataSource::getUsername, SimpleDriverDataSource::setUsername);
 			add(DataSourceProperty.PASSWORD, SimpleDriverDataSource::getPassword, SimpleDriverDataSource::setPassword);