The “JSON - Exception in server tick loop” error occurs when there’s a problem with your server’s .json files - specifically ops.json, whitelist.json, or usercache.json. Deleting these files and restarting your server will allow new, working versions to be created automatically. If you need help, our support team is always available
java.lang.NullPointerException: Exception in server tick loop
at net.minecraft.server.v1_7_R3.JsonList.load(JsonList.java:171)Log in to the ChipHead Panel.

Stop your server.

Go to the Files tab.

Select the following files and delete them:
ops.json
whitelist.json
usercache.json
Start your server again.

Your server will automatically generate new versions of these files, resolving the error.