Catch additional error on not existing custom column linked to read column (#2341)

Prevent metadata changes are lost on edit books with errors (#2326)
Better log output
Renamed log message on database delete

cps/templates/detail.html

@@ -295,7 +295,7 @@
       {% if g.user.role_edit() %}
       <div class="btn-toolbar" role="toolbar">
         <div class="btn-group" role="group" aria-label="Edit/Delete book">
-          <a href="{{ url_for('edit-book.edit_book', book_id=entry.id) }}" class="btn btn-sm btn-primary" id="edit_book" role="button"><span class="glyphicon glyphicon-edit"></span> {{_('Edit Metadata')}}</a>
+          <a href="{{ url_for('edit-book.show_edit_book', book_id=entry.id) }}" class="btn btn-sm btn-primary" id="edit_book" role="button"><span class="glyphicon glyphicon-edit"></span> {{_('Edit Metadata')}}</a>
         </div>
       </div>
       {% endif %}