use correct key

Author: cormacdalton

lib/mcapi/crypto/jwe-crypto.js

@@ -133,12 +133,12 @@ function JweCrypto(config) {
         decryptionEncoding = "AES-256-GCM";
         break;
       case "A128CBC-HS256":
-        decryptionEncoding = "AES-128-CBC";
-        secretKey = secretKey.slice(16, 32);
-        gcmMode = false;
         if(this.enableHmacVerification) {
           verifyCbcHmac(jweTokenParts[0], iv, encryptedText, authTag, secretKey);
         }
+        decryptionEncoding = "AES-128-CBC";
+        secretKey = secretKey.slice(16, 32);
+        gcmMode = false;
         break;
       default:
         throw new Error(