FGDC metadata extension with online linkage causes ClassCastException

[mattblanchette]

Attempting to add a FGDC metextns (Metadata Extension) element with an onlink (Online Linkage) in the metadata edit forms causes the following Error message:

Error
The requested operation could not be performed.
ClassCastException : java.util.ArrayList cannot be cast to java.lang.String

Once these elements (<metextns><onlink/></metextns>) are added to an FGDC metadata entry, it can no longer be opened for editing since it will always throw this Error.

Error log shows that this Exception originated from the addValues method of org.fao.geonet.kernel.EditLib class, which appears to be line 999 since it performs a String cast:
text.setAttribute(Edit.Attribute.Attr.VALUE, (String) values.get(i));

[mattblanchette]

Current workaround: Add test in addValues method:

if( values.get(i) instanceof String ) {
    Element text  = new Element(Edit.Element.Child.TEXT, Edit.NAMESPACE);
    text.setAttribute(Edit.Attribute.Attr.VALUE, (String) values.get(i));

    elem.addContent(text);
}

[ticheler]

Fixed and tested by Simon Pigot