Sent support a ticket about this, this is their response:
Greetings ARKS Operative,
Thank you for your time and effort for sending us your concern. We understand that there are some items in Unique Weapon Badge that has no Element on it. We do apologize for the inconvenience this has caused you. Please be informed that we will forward this to the relevant department for further consideration and improvement of the game. I kindly ask you to stay tuned to our official website and social media accounts with regards to this matter. We are truly grateful for people like you who patronize our game. If you have any other concerns feel free to contact us again.
This response seems very vague, as it doesn't even confirm if it's a bug or not...