Handle NPE on CopyPagesTo

DEVSIX-6298

Autoported commit.
Original commit hash: [30c6c9e88]

Author: AnhelinaM

itext.tests/itext.forms.tests/itext/forms/PdfFormCopyTest.cs

@@ -578,5 +578,19 @@ public virtual void MergeTwoWidgetsAndTwoWidgetsTest() {
             NUnit.Framework.Assert.IsNull(new CompareTool().CompareByContent(destFilename, cmpFileName, destinationFolder
                 , "diff_"));
         }
+
+        [NUnit.Framework.Test]
+        public virtual void WidgetContainsNoTEntryTest() {
+            String sourceFileName = sourceFolder + "fieldThreeWidgets.pdf";
+            String destFileName = destinationFolder + "widgetContainsNoTEntryTest.pdf";
+            String cmpFileName = sourceFolder + "cmp_widgetContainsNoTEntryTest.pdf";
+            PdfDocument sourcePdfDocument = new PdfDocument(new PdfReader(sourceFileName));
+            PdfDocument resultPdfDocument = new PdfDocument(new PdfWriter(destFileName));
+            sourcePdfDocument.CopyPagesTo(1, sourcePdfDocument.GetNumberOfPages(), resultPdfDocument, new PdfPageFormCopier
+                ());
+            resultPdfDocument.Close();
+            NUnit.Framework.Assert.IsNull(new CompareTool().CompareByContent(destFileName, cmpFileName, destinationFolder
+                , "diff_"));
+        }
     }
 }

itext.tests/itext.forms.tests/resources/itext/forms/PdfFormCopyTest/cmp_widgetContainsNoTEntryTest.pdf

@@ -315,7 +315,8 @@ private void AddChildToExistingParent(PdfDictionary fieldDic, ICollection<String
                 if (existingFields.Contains(name)) {
                     PdfArray kids = parent.GetAsArray(PdfName.Kids);
                     foreach (PdfObject kid in kids) {
-                        if (((PdfDictionary)kid).Get(PdfName.T).Equals(fieldDic.Get(PdfName.T))) {
+                        if (((PdfDictionary)kid).Get(PdfName.T) != null && ((PdfDictionary)kid).Get(PdfName.T).Equals(fieldDic.Get
+                            (PdfName.T))) {
                             PdfFormField kidField = MakeFormField(kid);
                             PdfFormField field = MakeFormField(fieldDic);
                             if (kidField == null || field == null) {

itext.tests/itext.forms.tests/resources/itext/forms/PdfFormCopyTest/fieldThreeWidgets.pdf

@@ -1 +1 @@
-22b28c21a6e4eba260a7470f015d7391d63cfbec
+30c6c9e883a50dae6adb0bfe884414f0d682cc31