Dzonia Lite Error: get_theme_data is deprecated since version 3.4…

Hi, I’ve suddenly got this random error appearing at the top of one of my websites that is using the Dzonia Lite theme. The error I’m receiving is:

Notice: get_theme_data is deprecated since version 3.4! Use wp_get_theme() instead. in /home/content/01/9485701/html/wp-includes/functions.php on line 2628

Warning: Cannot modify header information – headers already sent out by (output started at /home/content/9485701/html/wp-includes/functions.php:2628) in /home/content/01/9485701/html/wp-includes/pluggable.pho on line 881

Does anyone know how I could go about fixing this? Thanks in advance!