Steps to reproduce:

1. Using a clean, fully patched installation of eZ Publish 5.2/eZ Find 5.2, create a new class with the following attributes:

	Title [Text line], required, searchable
	Related content [Object relations], not required, searchable

2. Create an object (e.g. 12306_1) of that class, and use the "Object relations" attribute to relate to another object of the same class (e.g. 12306_2);
3. On the Solr admin interface - accessible on http://localhost:8983/solr/url by default - search for "12306". There should be two results, one for "12306_1" and one for "12306_2";
4. The XML structure for "12306_1" contains a "submeta_related_content" section:

...
<arr name="submeta_related_content___current_version_si">
  <int>1</int>
</arr>
...

...where current_version is 1, which is correct.

5. Create a new version of "12306_2";
6. Delete version 1 of "12306_2";
7. Re-index Solr;
8. On the Solr admin interface, search again for "12306". The resulting XML structure for "12306_1" no longer has a "submeta_related_content" section, which is wrong, since "12306_2" is still related to "12306_1".