Update PrivacyIDEA.java

fix nullPointerException

Author: lukasmatusiewicz

src/main/java/org/privacyidea/PrivacyIDEA.java

@@ -158,7 +158,7 @@ private PIResponse getPIResponse(String type, String input, String pass, Map<Str
         }
         String response = runRequestAsync(ENDPOINT_VALIDATE_CHECK, params, headers, false, POST);
         // Shutdown the scheduler if user successfully authenticated
-        if (this.parser.parsePIResponse(response).value)
+        if (this.parser.parsePIResponse(response) != null && this.parser.parsePIResponse(response).value)
         {
             this.scheduler.shutdownNow();
         }