I guess you or someone made a custom smarty tag named plugin and by not following PrestaShop's best practices of using modules and overrides, the custom smarty tag was coded into core files and by updating your shop, custom code went bye bye.
I don't know if that custom tag did something special, because there is a core PrestaShop hook that does the same.
This is how you properly register custom smarty tags.
Replace that code on line 38
{plugin module='ps_searchbar' hook='displayTop'}
with core tag
{hook h='displayTop' mod='ps_searchbar'}
A bit of googling and I found this. If your shop was using it, it's not needed anymore so fix your theme and replace {plugin} tags with core tags.