Add outlines with invalid parent links test

DEVSIX-3703

DEVSIX-4243

Autoported commit.
Original commit hash: [1d721562c]

Author: BlackEgoist

itext.tests/itext.kernel.tests/itext/kernel/pdf/PdfOutlineTest.cs

@@ -191,6 +191,19 @@ public virtual void UpdateOutlineTitle() {
                  + "cmp_" + filename, destinationFolder, "diff_"));
         }
 
+        [NUnit.Framework.Test]
+        public virtual void GetOutlinesInvalidParentLink() {
+            NUnit.Framework.Assert.That(() =>  {
+                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);
+            }
+            , NUnit.Framework.Throws.InstanceOf<NullReferenceException>())
+;
+        }
+
         [NUnit.Framework.Test]
         public virtual void ReadOutlineTitle() {
             String filename = sourceFolder + "updateOutlineTitleResult.pdf";

itext.tests/itext.kernel.tests/resources/itext/kernel/pdf/PdfOutlineTest/outlinesInvalidParentLink.pdf

@@ -1 +1 @@
-776c70918991e421af46bc730ebdb7bf647eafae
+1d721562c3563cdc12b0e86d75878c5f7e75acd1