‘llegal offset type in isset or empty in …on line 340’

Hey!

I’m attempting to show the values of two custom taxonomies while looping through custom post types. I’ve done it successfully for one of the two using this code:

$topic = get_the_terms($post->ID,array('taxonomy' => 'topic'));
if( !empty($topic) ):
	foreach($topic as $topics) {
		$color = get_field('topic-color', 'topic' . '_' . $topics->term_id);
		echo '<a class="current-research-button" style="border-color:' . $color . ';"href="' . get_category_link($topics->term_id) . '">' . $topics->name . '</a>';
} endif; ?>

If I add another variable for a second taxonomy, I get this error:

Warning: Illegal offset type in isset or empty in /Users/hobbes/Local Sites/detroitpeer/app/public/wp-includes/taxonomy.php on line 340

If I comment out the first variable ($topic) then the error goes away and the second taxonomy loop runs just fine.

What could be causing this?

The page I need help with: [log in to see the link]