Throw IllegalStateException when authtoken has not been generated

Change-Id: I408fe3032d6a4d2244c3d5d590b96ef74f9c9b4e
diff --git a/src/com/android/keychain/KeyChainService.java b/src/com/android/keychain/KeyChainService.java
index 19a55bd..940c427 100644
--- a/src/com/android/keychain/KeyChainService.java
+++ b/src/com/android/keychain/KeyChainService.java
@@ -82,7 +82,11 @@
             if (!isKeyStoreUnlocked()) {
                 throw new IllegalStateException("keystore locked");
             }
-            if (!mAccountManager.peekAuthToken(mAccount, alias).equals(authToken)) {
+            String peekedAuthToken = mAccountManager.peekAuthToken(mAccount, alias);
+            if (peekedAuthToken == null) {
+                throw new IllegalStateException("peekedAuthToken == null");
+            }
+            if (!peekedAuthToken.equals(authToken)) {
                 throw new IllegalStateException("authtoken mismatch");
             }
             String key = type + alias;