fix: don't try to sanitize null owners

src/backend/src/om/entitystorage/SetOwnerES.js

@@ -19,6 +19,7 @@
 const { get_user } = require("../../helpers");
 const { AppUnderUserActorType, UserActorType } = require("../../services/auth/Actor");
 const { Context } = require("../../util/context");
+const { nou } = require("../../util/langutil");
 const { BaseES } = require("./BaseES");
 
 class SetOwnerES extends BaseES {
@@ -64,6 +65,7 @@ class SetOwnerES extends BaseES {
         },
         async _sanitize_owner (entity) {
             let owner = await entity.get('owner');
+            if ( nou(owner) ) return null;
             owner = get_user({ id: owner });
             await entity.set('owner', owner);
         }

src/backend/src/util/langutil.js

@@ -26,6 +26,9 @@ const whatis = thing => {
     return typeof thing;
 };
 
+const nou = v => v === null || v === undefined;
+
 module.exports = {
     whatis,
+    nou,
 };