Try to add the following PHP code snippet to the child theme functions.php file to fix this

function basel_category_thumb_double_size( $category ) {
		global $basel_loop;
		$small_thumbnail_size  	= apply_filters( 'subcategory_archive_thumbnail_size', 'woocommerce_thumbnail' );
		$dimensions    			= wc_get_image_size( $small_thumbnail_size );
		$thumbnail_id  			= get_woocommerce_term_meta( $category->term_id, 'thumbnail_id', true  );
        $attr_height 			= '';

		if( ! empty( $basel_loop['double_size'] ) && $basel_loop['double_size'] ) {
			$small_thumbnail_size = 'shop_catalog_x2';
			$dimensions['width'] *= 2;
			if ( $dimensions['height'] ) {
				$dimensions['height'] *= 2;
				$attr_height = 'height="' . esc_attr( $dimensions['height'] ) . '"';
			}
		}

		if ( $thumbnail_id ) {
			$image = wp_get_attachment_image_src( $thumbnail_id, $small_thumbnail_size  );
			$image = $image[0];
		} else {
			$image = wc_placeholder_img_src();
		}

		if ( $image ) {
			// Prevent esc_url from breaking spaces in urls for image embeds
			// Ref: https://core.trac.wordpress.org/ticket/23605
			$image = str_replace( ' ', '%20', $image );

			echo '<img src="' . esc_url( $image ) . '" alt="' . esc_attr( $category->name ) . '" width="' . esc_attr( $dimensions['width'] ) . '" ' . $attr_height . ' />';
		}
	}