Fix ForeignKeyField not returning object when attribute is set and new object is created

aleksis/core/frontend/components/generic/forms/ForeignKeyField.vue

@@ -109,12 +109,13 @@ export default {
     handleSave(data) {
       let newItem =
         data.data[this.gqlCreateMutation.definitions[0].name.value].item;
-      let newValue = this.$attrs["return-object"] ? newItem : newItem.id;
-      let modelValue = this.$attrs.hasOwnProperty("multiple")
-        ? Array.isArray(this.$attrs.value)
-          ? this.$attrs.value.concat(newValue)
-          : [newValue]
-        : newValue;
+      let newValue = "return-object" in this.$attrs ? newItem : newItem.id;
+      let modelValue =
+        "multiple" in this.$attrs
+          ? Array.isArray(this.$attrs.value)
+            ? this.$attrs.value.concat(newValue)
+            : [newValue]
+          : newValue;
 
       this.$emit("input", modelValue);
     },