Past event presentations images: the text below it (“”Showing X of Y images”) is hidden sometimes

Example: https://dust03.bsc.es/news-events/events/1st-africa-middle-east-expert-meeting-and-workshop-on-the-health-impact-of-airborne-dust

Users should see this:

Instead of this:

The text below each image (p element with class "slider-img-number") is not visible because it is behind the image because the height of the "slider-img-item" is not enough

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Also change color of navigation arrows to white