Warning: json_encode() expects exactly 1 parameter, 2 given

I’m getting the following error in the source code on my Events page, which uses the most updated version of GigPress (http://www.amystewart.com/events/):

<script type="application/ld+json"><br />
<b>Warning</b>:  json_encode() expects exactly 1 parameter, 2 given in <b>[removed]/wp-content/plugins/gigpress/output/gigpress_shows.php</b> on line <b>288</b><br />
</script><!-- Generated by GigPress 2.3.16 -->

I have not modified that portion of the code, so it should not be generating an error. I also found that the error is very common among GigPress users when running a Google search for the “warning” terminology:
https://www.google.com/webhp?sourceid=chrome-instant&ion=1&espv=2&ie=UTF-8#q=json_encode()%20expects%20exactly%201%20parameter%2C%202%20given%20gigpress