Notice: Undefined offset: 1 in .../administrator/components/com_easyblog/includes/image/image.php on line 520
preg_match('/src="([^"]+)"/', $image, $src);
$url = $src;
In many cases, this preg_match returns no array, so $src is empty. Attempting to index into  thus fails. Here's the tag on an image that's not being converted to amp-img. It is found in the outer regex, but not the inner. Could it be that the img tag has a class before the src?
<img class='calloutplanet' src='https://www.retrograde.today/images/planetsretro/mars.png' alt='Mars' />