jsencrypt NULL OF DECRYPT. WHY?

Hey,i have a trouble in decrypt test,and result is NULL, here's my code: `var PUBLIC_KEY = "MIGfMA0GCSqGSIb3DQEBAQUAA4GNADCBiQKBgQDlOJu6TyygqxfWT7eLtGDwajtNFOb9I5XRb6khyfD1Yt3YiCgQWMNW649887VGJiGr/L5i2osbl8C9+WJTeucF+S76xFxdU6jE0NQ+Z+zEdhUTooNRaY5nZiu5PgDB0ED/ZKBUSLKL7eibMxZtMlUDHjm4gwQco1KRMDSmXSMkDwIDAQAB"; var PRIVATE_KEY = "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";

var data = "HELLO WORLD!";

//encrypt with public key var crypt = new JSEncrypt(); crypt.setPublicKey(PUBLIC_KEY); var enc = crypt.encrypt(data);

//decrypt with private key var decrypt = new JSEncrypt(); decrypt.setPrivateKey(PRIVATE_KEY); var dec = decrypt.decrypt(enc);

console.log(enc); console.log(dec);`

In my code, Encrypt can work,but decrypt can not work. `/Users/ddx-b3/.nvm/versions/node/v5.6.0/bin/node JSEncrypt.js diHn2PO1QS2H0ctSMcI7kMLMLiDRHvq3oNE9DlWdkEpZMtpEqlG/zprfaIA0ajsaucqqHnotqNxopFjG7JiKMtAeOAI92hXcqQp35FUeSDeixK9vAkgCT5xy1bgLd0j/hior+Z5zVIf7tpfnK01W7ZMAvPxqemCPEde9FJuirX8= null

Process finished with exit code 0`