use fallback language for when translation is empty

i18n.config.ts

@@ -1,3 +1,5 @@
+import type { LocaleMessage } from "@intlify/core";
+import type { VueMessageType } from "vue-i18n";
 import de from "./locales/de.json";
 import en from "./locales/en.json";
 import nb from "./locales/nb.json";
@@ -15,24 +17,48 @@ import pt from "./locales/pt.json";
 import ro from "./locales/ro.json";
 import ru from "./locales/ru.json";
 
+function cleanupEmptyProperties(obj: any, fallback: any): any {
+  Object.keys(obj).forEach((key) => {
+    if (typeof obj[key] === "object") {
+      obj[key] = cleanupEmptyProperties(obj[key], fallback[key]);
+    }
+    if (obj[key] === "") {
+      obj[key] = fallback[key];
+    }
+  });
+  return obj;
+}
+
+function cleanup(
+  locale: LocaleMessage<VueMessageType>,
+  fallback: LocaleMessage<VueMessageType>,
+): LocaleMessage<VueMessageType> {
+  Object.keys(locale).forEach((key) => {
+    if (typeof locale[key] === "object") {
+      locale[key] = cleanupEmptyProperties(locale[key], fallback[key]);
+    }
+  });
+  return locale;
+}
+
 export default defineI18nConfig(() => ({
   legacy: false,
   messages: {
-    nb,
+    nb: cleanup(nb, en),
     en,
-    de,
-    nl,
-    fr,
-    sl,
-    tr,
-    ta,
-    da,
-    es,
-    et,
-    fi,
-    hu,
-    pt,
-    ro,
-    ru,
+    de: cleanup(de, en),
+    nl: cleanup(nl, en),
+    fr: cleanup(fr, en),
+    sl: cleanup(sl, en),
+    tr: cleanup(tr, en),
+    ta: cleanup(ta, en),
+    da: cleanup(da, en),
+    es: cleanup(es, en),
+    et: cleanup(et, en),
+    fi: cleanup(fi, en),
+    hu: cleanup(hu, en),
+    pt: cleanup(pt, en),
+    ro: cleanup(ro, en),
+    ru: cleanup(ru, en),
   },
 }));