Fix invariant violation error with unique key

React <table> cannot handle when you dynamically change the columns in the table. This is because React tries to only re-render parts of a component that have changed, which gets all wonky with tables. Fortunately, React components can be given a key id. If the key changes, then the entire component is re-rendered. Giving the CategoriesTable a unique key for the id of the user's profile page makes this go away!