Attempt to fix bigint serialization issue (#1501)

## Description:

Attempt to fix bigint serialization issue

## Please complete the following:

- [x] I have added screenshots for all UI updates
- [x] I process any text displayed to the user through translateText()
and I've added it to the en.json file
- [x] I have added relevant tests to the test directory
- [ ] I confirm I have thoroughly tested these changes and take full
responsibility for any bugs introduced
- [ ] I have read and accepted the CLA aggreement (only required once).

src/core/StatsSchemas.ts

@@ -89,7 +89,7 @@ export const OTHER_INDEX_LOST = 3; // Structures/warships destroyed/captured by
 export const OTHER_INDEX_UPGRADE = 4; // Structures upgraded
 
 const BigIntStringSchema = z.preprocess((val) => {
-  if (typeof val === "string" && /^\d+$/.test(val)) return BigInt(val);
+  if (typeof val === "string" && /^-?\d+$/.test(val)) return BigInt(val);
   if (typeof val === "bigint") return val;
   return val;
 }, z.bigint());