Removed copying of dueDate since null values are not supported.

client/src/components/Card/ActionsStep.jsx

@@ -61,7 +61,9 @@ const ActionsStep = React.memo(
     defaultPath.listId = card.listId;
     defaultPath.cardId = card.id;
     defaultPath.name = card.name;
+    if (card.dueDate !== null) {
       defaultPath.dueDate = card.dueDate;
+    }
     defaultPath.stopwatch = card.stopwatch;
     defaultPath.labels = card.labels;
     defaultPath.boardMemberships = boardMemberships;

client/src/components/CardCopyStep/CardCopyStep.jsx

@@ -35,7 +35,7 @@ const CardCopyStep = React.memo(
       attachments: defaultPath.attachments,
       labels: defaultPath.labels,
       users: defaultPath.users,
-      dueDate: defaultPath.dueDate,
+      // dueDate: defaultPath.dueDate,
       ...defaultPath,
     }));