Fix chat layout height under messages tab

## Summary The chat layout height under the messages tab is broken. It works on mobile but requires scrolling. The layout should fit the screen without scrolling. ## Steps to Reproduce Not provided. ## Expected Behaviour The chat layout should fit the screen without requiring scrolling, similar to a decent app like Snek. ## Actual Behaviour The chat layout height is broken; on mobile it works but requires scrolling. ## Environment Not provided. --- *Reported by **retoor** via DevPlace.*