问谷歌市场许可中的NullPointerException

EN

10-11 23:44:04.220 E/AndroidRuntime(15090): java.lang.NullPointerException
10-11 23:44:04.220 E/AndroidRuntime(15090):     at com.android.vending.licensing.LicenseValidator.verify(LicenseValidator.java:101)
10-11 23:44:04.220 E/AndroidRuntime(15090):     at com.android.vending.licensing.LicenseChecker$ResultListener$2.run(LicenseChecker.java:213)
10-11 23:44:04.220 E/AndroidRuntime(15090):     at android.os.Handler.handleCallback(Handler.java:615)
10-11 23:44:04.220 E/AndroidRuntime(15090):     at android.os.Handler.dispatchMessage(Handler.java:92)
10-11 23:44:04.220 E/AndroidRuntime(15090):     at android.os.Looper.loop(Looper.java:137)
10-11 23:44:04.220 E/AndroidRuntime(15090):     at android.os.HandlerThread.run(HandlerThread.java:60)

public void verify(PublicKey publicKey, int responseCode, String signedData, String signature) {
    String userId = null;
    // Skip signature check for unsuccessful requests
    ResponseData data = null;
    if (responseCode == LICENSED || responseCode == NOT_LICENSED ||
            responseCode == LICENSED_OLD_KEY) {
        // Verify signature.
        try {
            Signature sig = Signature.getInstance(SIGNATURE_ALGORITHM);
            sig.initVerify(publicKey);
            sig.update(signedData.getBytes());