The first argument should be an array in sites/all/modules/requestinvitation/requestinvitation.module on line 246.

I get the same error and see it repeated several times for just one invitation request.

same for me, i commented out the
//$value = array_keys(array_filter($value));

line and it half works, except there is no checkbox rendered for the first invite...

Same Problem here - any other hints than #3?! Cause i think commenting a line out is the wrong way to fix a/that bug :)

I was out of touch for some time. Will look at this asap.

Replace line 246 with:

if (is_array($value) && isset($values['array_filter'])) {
$value = array_keys(array_filter($value));
}

Worked for me.

martysmind comment#6 worked for me also
maybe should be considered a patch, or a fix... this is why this community rules

Thanks. I will add the fix.

Fix is added to the repo but still not made to a release. Let me know if there's any issue with the patch before a new release.

does #6 work?