Editing EPrints 3.4.3 (section)

==== Non-multiple Subject field causes an internal server error ====
This problem does not affect any fields in a vanilla installation of EPrints 3.4.3 but will affect any non-multiple [[Subject field]]s unless they use the <code>Field::Subject</code> typed component in the workflow.  From the web browser the page will just show an internal server error but the underling error message in the webserver logs will be something like:

 [Fri Sep 10 10:54:00.439169 2021] [:error] [pid 12763] Can't use an undefined value as an ARRAY reference at /opt/eprints3/perl_lib/EPrints/MetaField/Subject.pm line 128.\n

This issue was caused by some recently introduced code to attempt to harmonise the behaviour of Subject fields independent of whether they use the <code>Field::Subject</code> workflow component.  Specifically, that any subject that has been made undepositable but which had already been selected for an item, should still appear an remain selected.  This prevent a user deselecting this option without realisng, whilst editing it for another reason. The <code>divisions</code> is a good example, where an institution has changed its structure and does not want users to deposit against old divisions but wants to ensure these old divisions remain associated with historical items. (see https://github.com/eprints/eprints3.4/issues/144 for more details).  

[https://github.com/eprints/eprints3.4/commit/41f6f199d7abb753a3d180aabde6a0c482825ff8 This patch] fixes this issue by checking to see whether the value returned by the <code>get_value</code> for the specific field, is already an ARRAY reference and if not making sure it is converted to one before the <code>foreach</code> code block that iterates over this value.