Price filter does not show in shop page

I wrote a custom theme for woocommerce and when I put the price filter in the sidebar, it does not show up. Every other filter shows up and works correctly like attributes. But the price filter does not.

I get this error:

Notice: Trying to get property of non-object in G:MAMPhtdocswpwp-contentpluginswoocommerceincludeswidgetsclass-wc-widget-price-filter.php on line 77

This is the code in line 77:

// If there are not posts and we're not filtering, hide the widget.
if ( ! WC()->query->get_main_query()->post_count && ! isset( $_GET['min_price'] ) && ! isset( $_GET['max_price'] ) ) { // WPCS: input var ok, CSRF ok.
        return;
    }

I know that the woocommerce uses the page template for showing the shop page and when I convert to another theme like storefront, the price filter works correctly. There is nothing wrong in my page.php file and the other contents just look fine in it.