Fix Wekan JSON import bug

If not all users are mapped the import crashes.

models/customFields.js

@@ -69,24 +69,28 @@ CustomFields.attachSchema(
        * should we show on the cards this custom field
        */
       type: Boolean,
+      defaultValue: false,
     },
     automaticallyOnCard: {
       /**
        * should the custom fields automatically be added on cards?
        */
       type: Boolean,
+      defaultValue: false,
     },
     alwaysOnCard: {
       /**
        * should the custom field be automatically added to all cards?
        */
       type: Boolean,
+      defaultValue: false,
     },
     showLabelOnMiniCard: {
       /**
        * should the label of the custom field be shown on minicards?
        */
       type: Boolean,
+      defaultValue: false,
     },
     createdAt: {
       type: Date,

models/wekanCreator.js

@@ -258,8 +258,9 @@ export class WekanCreator {
     // now add other members
     if (boardToImport.members) {
       boardToImport.members.forEach(wekanMember => {
-        // do we already have it in our list?
+        // is it defined and do we already have it in our list?
         if (
+          wekanMember.wekanId &&
           !boardToCreate.members.some(
             member => member.wekanId === wekanMember.wekanId,
           )