Bug #1925378: Error when trying to edit Undefined Date

src/calibre/gui2/library/delegates.py

@@ -247,6 +247,8 @@ class DateDelegate(QStyledItemDelegate, UpdateEditorGeometry):  # {{{
             val = now()
         else:
             val = index.data(Qt.ItemDataRole.EditRole)
+            if is_date_undefined(val):
+                val = now()
         editor.setDateTime(val)
 
 # }}}

src/calibre/utils/date.py

@@ -157,6 +157,8 @@ safeyear = lambda x: min(max(x, MINYEAR), MAXYEAR)
 
 def qt_to_dt(qdate_or_qdatetime, as_utc=True):
     o = qdate_or_qdatetime
+    if o is None:
+        return UNDEFINED_DATE
     if hasattr(o, 'toUTC'):
         # QDateTime
         o = o.toUTC()