fix(stronghold): return null if there is no record (#129)

* [stronghold] return null if there is no record

* Return value

* return statement

* prettier

* fix function signature

* fix if condition

* simplify condition

---------

Co-authored-by: Fabian-Lars <fabianlars@fabianlars.de>

plugins/stronghold/guest-js/index.ts

@@ -293,12 +293,18 @@ export class Store {
     this.client = client;
   }
 
-  async get(key: StoreKey): Promise<Uint8Array> {
+  async get(key: StoreKey): Promise<Uint8Array | null> {
     return await invoke<number[]>("plugin:stronghold|get_store_record", {
       snapshotPath: this.path,
       client: this.client,
       key: toBytesDto(key),
-    }).then((v) => Uint8Array.from(v));
+    }).then((v) => {
+      if (v) {
+        return Uint8Array.from(v);
+      } else {
+        return null;
+      }
+    });
   }
 
   async insert(