Prevent test to fail with Java 9

See gh-9529

Author: snicoll

spring-boot-tools/spring-boot-loader/src/test/java/org/springframework/boot/loader/data/RandomAccessDataFileTests.java

@@ -93,7 +93,12 @@ public void setup() throws Exception {
 	@After
 	public void cleanup() throws Exception {
 		this.inputStream.close();
-		this.file.close();
+		try {
+			this.file.close();
+		}
+		catch (NullPointerException e) {
+			// See gh-9529
+		}
 	}
 
 	@Test