JS error affecting product image gallery

Hello!

I’m developing a theme and added support to the new WooCommerce Product Gallery. But this plugin is throwing a JavaScript error, and because of that, the gallery zoom doesn’t work the first the image time is hovered. The gallery works fine when I deactivate the plugin.

Everything is updated:
WP 4.9.7
WooCommerce 3.4.3
WooCommerce Expand Tabs 1.7

Here’s the log:

Uncaught TypeError: Cannot read property 'indexOf' of undefined
    at _.fn.init._.fn.load (jquery.js:9857)
    at HTMLImageElement.<anonymous> (single-product.js?ver=1.4:172)
    at Function.each (jquery.js:354)
    at _.fn.init.each (jquery.js:189)
    at ProductGallery.initFlexslider (single-product.js?ver=1.4:170)
    at new ProductGallery (single-product.js?ver=1.4:115)
    at _.fn.init.$.fn.wc_product_gallery (single-product.js?ver=1.4:293)
    at HTMLDivElement.<anonymous> (single-product.js?ver=1.4:301)
    at Function.each (jquery.js:354)
    at _.fn.init.each (jquery.js:189)

/wp-content/plugins/woocommerce-extend-tabs/wc30/single-product.js?ver=1.4

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