Make objectForm implicitly handle undefined isCreate

depending on the presence of editItem.

For the rationale see comment in change.

CHANGELOG.rst

@@ -14,6 +14,7 @@ Changed
 
 * Announcements are shown in calendar.
 * DialogObjectForm is now slightly wider.
+* [Dev] DialogObjectForm now implicitly handles a missing isCreate-prop depending on the presence of editItem.
 
 Fixed
 ~~~~~

aleksis/core/frontend/mixins/createOrPatchPropsMixin.js

@@ -15,7 +15,7 @@ export default {
     isCreate: {
       type: Boolean,
       required: false,
-      default: true,
+      default: undefined,
     },
     /**
      * The graphQL create mutation

aleksis/core/frontend/mixins/objectFormMixin.js

@@ -55,6 +55,13 @@ export default {
       this.resetModel();
     },
     resetModel() {
+      // Handle isCreate undefined, by deciding on the presence of editItem
+      //   This implicit behaviour often makes more sense
+      //   and doing it higher up (in parent) makes parent less flexible.
+      //   Specifically not working anymore with CRUD.
+      if (!this.isCreate) {
+        this.isCreate = !this.editItem;
+      }
       this.itemModel = JSON.parse(
         JSON.stringify(this.isCreate ? this.defaultItem : this.editItem),
       );