diff --git a/src/PdfCreator.ts b/src/PdfCreator.ts
index ce3d430..3b21eab 100644
--- a/src/PdfCreator.ts
+++ b/src/PdfCreator.ts
@@ -246,6 +246,10 @@ export class PdfCreator {
             return null;
         }
 
-        return [array[1], array[0]].concat(this.swapArrayPairs(array.slice(2)));
+        const rest = this.swapArrayPairs(array.slice(2))
+        if (!rest) {
+            return [array[1], array[0]]
+        }
+        return [array[1], array[0]].concat(rest);
     }
 }
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