Fix DataSourceHealthIndicator test failure

Fix failure introduced in commit 8af02ce0.

See gh-11880

spring-boot-project/spring-boot-actuator/src/main/java/org/springframework/boot/actuate/jdbc/DataSourceHealthIndicator.java

@@ -86,7 +86,7 @@ public class DataSourceHealthIndicator extends AbstractHealthIndicator
 		super("DataSource health check failed");
 		this.dataSource = dataSource;
 		this.query = query;
-		this.jdbcTemplate = new JdbcTemplate(dataSource);
+		this.jdbcTemplate = (dataSource == null ? null : new JdbcTemplate(dataSource));
 	}
 
 	@Override