Fix for RelatedModelField (#6657)

- Cache initial data in memo
- Fixes https://github.com/inventree/InvenTree/issues/6654

src/frontend/src/components/forms/fields/RelatedModelField.tsx

@@ -43,6 +43,7 @@ export function RelatedModelField({
 
   const [offset, setOffset] = useState<number>(0);
 
+  const [initialData, setInitialData] = useState<{}>({});
   const [data, setData] = useState<any[]>([]);
   const dataRef = useRef<any[]>([]);
 
@@ -61,17 +62,15 @@ export function RelatedModelField({
       const url = `${definition.api_url}${field.value}/`;
 
       api.get(url).then((response) => {
-        const data = response.data;
-
-        if (data && data.pk) {
+        if (response.data && response.data.pk) {
           const value = {
-            value: data.pk,
-            data: data
+            value: response.data.pk,
+            data: response.data
           };
 
-          setData([value]);
+          setInitialData(value);
           dataRef.current = [value];
-          setPk(data.pk);
+          setPk(response.data.pk);
         }
       });
     } else {
@@ -208,10 +207,14 @@ export function RelatedModelField({
     };
   }, [definition]);
 
-  const currentValue = useMemo(
-    () => pk !== null && data.find((item) => item.value === pk),
-    [pk, data]
-  );
+  const currentValue = useMemo(() => {
+    if (!pk) {
+      return null;
+    }
+
+    let _data = [...data, initialData];
+    return _data.find((item) => item.value === pk);
+  }, [pk, data]);
 
   // Field doesn't follow Mantine theming
   // Define color theme to pass to field based on Mantine theme
@@ -278,7 +281,6 @@ export function RelatedModelField({
         onMenuScrollToBottom={() => setOffset(offset + limit)}
         onMenuOpen={() => {
           setIsOpen(true);
-          setValue('');
           resetSearch();
           selectQuery.refetch();
         }}