Customizing Error

I’ve got the secondary child theme activated and haven’t done much editing yet. When I click ‘customize’ under Appearance the preview area displays this text:

Warning: Creating default object from empty value in /home/bridgearts/www/www/wp-content/themes/symphony/theme/class-symphony-customizer.php on line 190

Fatal error: Cannot use object of type stdClass as array in /home/bridgearts/www/www/wp-content/themes/symphony/theme/class-symphony-customizer-theme-helper.php on line 573

Would be grateful if anyone could explain why this is happening. It doesn’t seem to affect the editing at this point but don’t want to get heavily into updating my site to find this theme is going to be problematic.