Update AesEncryptionHelper length check for NET8_0_OR_GREATER

Author: BobLd

src/UglyToad.PdfPig/Encryption/AesEncryptionHelper.cs

@@ -27,13 +27,13 @@ public static byte[] Decrypt(byte[] data, byte[] finalKey)
                 aes.IV = iv;
 
 #if NET8_0_OR_GREATER
-                var encryptedData = data.AsSpan(iv.Length);
-                if (encryptedData.IsEmpty)
+                if (data.Length <= iv.Length)
                 {
                     aes.Clear();
                     return [];
                 }
 
+                var encryptedData = data.AsSpan(iv.Length);
                 var output = aes.DecryptCbc(encryptedData, iv, PaddingMode.PKCS7);
                 aes.Clear();
                 return output;