Inherited memberships not created correctly when contact count changes.

Suppose you have an organization membership.  Suppose the organization has 4 related contacts, each of whom inherits the membership.

Suppose you then add a related contact.

Suppose you then renew the membership.

The newly related contact does not receive the inherited membership.  In fact, each time you save / update the membership, an apparently random set of 4 related contacts receives the inherited membership.

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This turns out to be a bug in Member/BAO/Membership.php. At line 1445, we see

if ($relMembership->find(TRUE)) {
  $params['id'] = $relMemIds['membership'] = $relMembership->id;
}

However, params['id'] is never initialized, so if some related memberships are not found, they are assigned the ID from the last iteration through the loop – meaning the previous contact loses their membership.  

The solution is to add $params['id'] = NULL right before.  (It would probably be better to set $params = NULL at the beginning of the loop, but I haven't tested that.)

I haven't submitted a patch, but it should be straightforward.