NullPointerException in XMLCipher with BC AES GCM NoPadding

I encountered a NullPointerException when using the XMLCipher#encryptData(org.w3c.dom.Document, org.w3c.dom.Element, java.lang.String, java.io.InputStream) method in conjunction with BC AES GCM NoPadding.

If the input data is not a multiple of the AES block size If the input data is 1-15 bytes larger than the initial buffer of 8192 bytes, the BC implementation returns null. This behavior is consistent with the JDK SPI javax.crypto.Cipher#update(byte[], int, int), which states:

Returns:
the new buffer with the result, or null if the underlying cipher is a block cipher and the input data is too short to result in a new block.

However, this leads to a NullPointerException in XMLCipher.

Steps to Reproduce

1. Provide a byte array which is not a multiple of AES block size Provide a byte array which is 1-15 bytes larger than the buffer of 8192 bytes
2. Initialize XMLCipher
3. Try to encrypt data

Code snippet

Security.insertProviderAt(new BouncyCastleProvider(), 1);

KeyGenerator generator = KeyGenerator.getInstance("AES", BouncyCastleProvider.PROVIDER_NAME);
generator.init(128);
SecretKey sessionKey = generator.generateKey();

XMLCipher xmlCipher = XMLCipher.getInstance(XMLCipher.AES_128_GCM);
xmlCipher.init(XMLCipher.ENCRYPT_MODE, sessionKey);

SOAPMessage soapMsg = loadSoapMsg();
Document soapDoc = soapMsg.getSOAPPart().getOwnerDocument();
EncryptedData data = xmlCipher.encryptData(soapDoc, null, new ByteArrayInputStream(dataToEncrypt));

Expected Result:

The encrypted cipher text

Actual Result

NullPointerException

Hints

I debugged the code and found a potential issue here

try (ByteArrayOutputStream baos = new ByteArrayOutputStream()) {
    while ((numBytes = serializedData.read(buf)) != -1) {
        byte[] data = c.update(buf, 0, numBytes);
        baos.write(data);
    }
    baos.write(c.doFinal());
    encryptedBytes = baos.toByteArray();
}

I assume that one only needs to wrap baos.write(data) in an if statement and doFinal encrypts the remaining bytes:

if (data != null) {
    baos.write(data);
}