implemented bill update

app/bills/[id]/edit/page.tsx

@@ -1,4 +1,4 @@
-import { Location } from '@/app/lib/db-types';
+import { PlainLocation, PlainBill, MongoLocation } from '@/app/lib/db-types';
 import clientPromise from '@/app/lib/mongodb';
 import { BillEditForm } from '@/app/ui/BillEditForm';
 import { ObjectId } from 'mongodb';
@@ -9,9 +9,28 @@ const fetchBillById = async (locationID:string, billID:string) => {
     const db = client.db("rezije");
 
     // find a location with the given locationID
-    const billLocation = await db.collection<Location>("lokacije").findOne({ _id: locationID })
+    const billLocation = await db.collection<MongoLocation>("lokacije").findOne({ _id: locationID })
+
+    if(!billLocation) {
+        console.log(`Location ${locationID} not found`);
+        return(null);
+    }
+
     // find a bill with the given billID
-    return(billLocation?.bills.find(({ _id }) => _id.toString() === billID))
+    const mongoBill = billLocation?.bills.find(({ _id }) => _id.toString() === billID);
+
+    if(!mongoBill) {
+        console.log('Bill not found');
+        return(null);
+    }
+
+    const { _id, ...billBase  } = mongoBill;
+
+    return({
+        id: _id.toString(),
+        ...billBase
+    } as PlainBill);
+
 }
 
 export default async function Page({ params:{ id } }: { params: { id:string } }) {
@@ -21,7 +40,6 @@ export default async function Page({ params:{ id } }: { params: { id:string } })
     const bill = await fetchBillById(invoiceID, billID);
 
     if (!bill) {
-        console.log('Bill not found');
         notFound();
     }
     return (