fieldgroup and empty value in child field

hi there,

my question is:
i have a fieldgroup "text-img-slide" with child fields "text", "image", and the child fields are optiona.
i create carousels with that.
for certain reasons i read the flexicontent-item's child fields' values into a php array and work with that.

problem-example:
slide 1 / fieldgroup-element 1 has a missing image.
that leads to: the seconds image lands in the first array element, because flexicontent (in my setup) does not store an empty value for the empty image in the fieldgroup's first element.

my question:
Can I configure the groupfield, or the child fields to save a null-value or similar in case of empty value?

I hope you can understand the scenario, thanks for reading,
Benjamin