Fix user count retrieval in stats router to handle potential null values

apps/infoalloggi/src/server/api/routers/stats.ts

@@ -76,14 +76,17 @@ export const statsRouter = createTRPCRouter({
       value: parseInt(String(item.value)),
     }));
 
-    const userCount = await db
-      .selectFrom("users")
-      .select((eb) => [eb.fn.count<number>("id").as("count")])
-      .executeTakeFirstOrThrow();
+    const userCount =
+      (
+        await db
+          .selectFrom("users")
+          .select((eb) => [eb.fn.count<number>("id").as("count")])
+          .executeTakeFirst()
+      )?.count || 0;
 
     return {
       userTimeserie,
-      userCount: userCount.count,
+      userCount,
       contattiTimeserie,
       serviziTimeserie,
     };