[BUG] Image zooming not working for galleries after image is changed

[sharif1093]

Current behavior

Image zooming works on the first image in an image gallery. But when the image is changed, either by selecting another image or letting the timer change the image in an autoplay mode, image zooming won't work on the newer image.

Expected behavior

Image zooming should work reliably on all images in an image gallery even after image is changed.

Steps to reproduce

1. Copy the image gallery code below:

```gallery(autoplay=3000)
https://source.unsplash.com/NQSWvyVRIJk/800x599
https://source.unsplash.com/zh7GEuORbUw/600x799
https://source.unsplash.com/PpOHJezOalU/800x599
https://source.unsplash.com/I1ASdgphUH4/800x599
```

2. Click on the first image that is display to zoom it. It should work.
3. Wait for a few seconds for the image to change, or change it manually.
4. Click on the new image to zoom. It won't work.

Environment

• Version: 0.11.15
• OS Version and name: Ubuntu 16.04 Xenial