reference to issue added (#5911)

CHANGELOG.md

@@ -27,7 +27,7 @@ We refer to [GitHub issues](https://github.com/JabRef/jabref/issues) by using `#
 - We fixed an issue where an erroneous "The library has been modified by another program" message was shown when saving. [#4877](https://github.com/JabRef/jabref/issues/4877)
 - We fixed an issue where the file extension was missing after downloading a file (we now fall-back to pdf). [#5816](https://github.com/JabRef/jabref/issues/5816)
 - We fixed an issue where cleaning up entries broke web URLs, if "Make paths of linked files relative (if possible)" was enabled, which resulted in various other issues subsequently. [#5861](https://github.com/JabRef/jabref/issues/5861)
-- We fixed an issue where the tab "Required fields" of the entry editor did not show all required fields, if at least two of the defined required fields are linked with a logical or.
+- We fixed an issue where the tab "Required fields" of the entry editor did not show all required fields, if at least two of the defined required fields are linked with a logical or. [#5859](https://github.com/JabRef/jabref/issues/5859)
 - We fixed several issues concerning managing external file types: Now everything is usable and fully functional. Previously, there were problems with the radio buttons, with saving the settings and with loading an input field value. Furthermore, different behavior for Windows and other operating systems was given, which was unified as well. [#5846](https://github.com/JabRef/jabref/issues/5846)
 
 ### Removed