if i have images from fields which are restricted to only 1 file, $image gets never defined, because the check with "has" on these fields returns false.
see https://github.com/conclurer/TextformatterSrcset/blob/master/TextformatterSrcset.module#L135
i fixed it for me with the following changes, but did not test it with other fields (so, no pull request for this).
// find the field that holds the image
if (!count($p->get($field->name))) continue;
$image = ($p->get($field->name)->name) ? $p->get($field->name) : $p->get($field->name)->get('name=' . $meta['imageName'] . '.' . $meta['ext']);