NPE when saving list property with null first

Caused by: java.lang.NullPointerException
at org.nuxeo.ecm.core.storage.BaseDocument.writeComplexProperty(BaseDocument.java:814)
at org.nuxeo.ecm.core.storage.BaseDocument.writeComplexProperty(BaseDocument.java:748)
at org.nuxeo.ecm.core.storage.sql.coremodel.SQLDocumentLive.writeDocumentPart(SQLDocumentLive.java:176)
at org.nuxeo.ecm.core.api.DocumentModelFactory.writeDocumentModel(DocumentModelFactory.java:236)
at org.nuxeo.ecm.core.api.AbstractSession.writeModel(AbstractSession.java:366)
at org.nuxeo.ecm.core.api.AbstractSession.saveDocument(AbstractSession.java:1529)
at com.nuxeo.pleiade.diffusion.web.mail.MailActionsBean.saveCurrentEmail(MailActionsBean.java:352)

                        if (list.isEmpty()) {
                            array = new Object[0];
                        } else {
                            // use properly-typed array, useful for mem backend that doesn't re-convert all types
                            Class<?> klass = list.get(0).getClass();
                            array = (Object[]) Array.newInstance(klass, list.size());
                        }

                            Class<?> klass = Object.class;
                            for (Object o : ar) {
                                if (o != null) {
                                    klass = o.getClass();
                                    break;
                                }
                            }