Add outlines with invalid parent links test

DEVSIX-3703

DEVSIX-4243

Author: BlackEgoist

kernel/src/test/java/com/itextpdf/kernel/pdf/PdfOutlineTest.java

@@ -216,6 +216,16 @@ public void updateOutlineTitle() throws IOException, InterruptedException {
         Assert.assertNull(new CompareTool().compareByContent(destinationFolder + filename, sourceFolder + "cmp_" + filename, destinationFolder, "diff_"));
     }
 
+    @Test
+    public void getOutlinesInvalidParentLink() throws IOException, InterruptedException {
+        junitExpectedException.expect(NullPointerException.class);
+        PdfReader reader = new PdfReader(sourceFolder + "outlinesInvalidParentLink.pdf");
+        String filename = "updateOutlineTitleInvalidParentLink.pdf";
+        PdfWriter writer = new PdfWriter(destinationFolder + filename);
+        PdfDocument pdfDoc = new PdfDocument(reader, writer);
+        PdfOutline outlines = pdfDoc.getOutlines(false);
+    }
+
     @Test
     public void readOutlineTitle() throws IOException {
         String filename = sourceFolder + "updateOutlineTitleResult.pdf";