Add null check on producer string

Kevin · iText-CI · commit 8104aac955ef · 2021-02-18T13:27:54.000Z
Closes #69.

Autoported commit.
Original commit hash: [090af8f2c]
diff --git a/itext/itext.kernel/itext/kernel/pdf/PdfDocument.cs b/itext/itext.kernel/itext/kernel/pdf/PdfDocument.cs
@@ -2271,7 +2271,8 @@ private void UpdateProducerInInfoDictionary() {
             }
             else {
                 if (info.GetPdfObject().ContainsKey(PdfName.Producer)) {
-                    producer = info.GetPdfObject().GetAsString(PdfName.Producer).ToUnicodeString();
+                    PdfString producerPdfStr = info.GetPdfObject().GetAsString(PdfName.Producer);
+                    producer = producerPdfStr != null ? producerPdfStr.ToUnicodeString() : null;
                 }
                 producer = AddModifiedPostfix(producer);
             }
diff --git a/port-hash b/port-hash
@@ -1 +1 @@
-075fb5390c140ce7710427fbbb526115706d61ef
+090af8f2c31512fb80c559ee5dd60c15ee97fc28

Original file line number	Diff line number	Diff line change
`@@ -2271,7 +2271,8 @@ private void UpdateProducerInInfoDictionary() {`
`2271`	`2271`	`}`
`2272`	`2272`	`else {`
`2273`	`2273`	`if (info.GetPdfObject().ContainsKey(PdfName.Producer)) {`
`2274`		`- producer = info.GetPdfObject().GetAsString(PdfName.Producer).ToUnicodeString();`
	`2274`	`+ PdfString producerPdfStr = info.GetPdfObject().GetAsString(PdfName.Producer);`
	`2275`	`+ producer = producerPdfStr != null ? producerPdfStr.ToUnicodeString() : null;`
`2275`	`2276`	`}`
`2276`	`2277`	`producer = AddModifiedPostfix(producer);`
`2277`	`2278`	`}`