$dbc is returning false. Your query has an error in it:
SELECT users.*, profile.* –You do not join with profile anywhere.
INNER JOIN contact_info
ON contact_info.user_id = users.user_id
The fix for this in general has been described by Raveren.
The query either returned no rows or is erroneus, thus FALSE is returned. Change it to
if (!$dbc || mysqli_num_rows($dbc) == 0)
Returns TRUE on success or FALSE on
failure. For SELECT, SHOW, DESCRIBE or
EXPLAIN mysqli_query() will return a