fix(config): sanitize config failing on array with multiple problems (@fehmer) (monkeytypegame#7221)

Sanitize throws error if an object contains an array with 1) an invalid
value and 2) too few items. The list of problems contains the path to
the array twice and tries to remove the invalid element from the already
deleted array.

Config object:

```json
 "customPolyglot": [
   "japanese"
 ]
```

Author: fehmer

frontend/__tests__/utils/sanitize.spec.ts

@@ -151,6 +151,18 @@ describe("sanitize function", () => {
           optional: { name: "Alice", age: 23 },
         },
       },
+      {
+        input: {
+          name: "Alice",
+          //results in two errors on the same path. array with invalid value and not enough items
+          enumArray: ["invalid" as any],
+        },
+        expected: {
+          mandatory: false,
+          partial: { name: "Alice" }, //enumArray is removed
+          optional: false,
+        },
+      },
     ];
 
     it.for(testCases)("object mandatory with $input", ({ input, expected }) => {

frontend/src/ts/utils/sanitize.ts

@@ -1,9 +1,12 @@
 import { z } from "zod";
 
 function removeProblems<T extends object | unknown[]>(
-  obj: T,
+  obj: T | undefined,
   problems: (number | string)[],
 ): T | undefined {
+  //already removed
+  if (obj === undefined) return undefined;
+
   if (Array.isArray(obj)) {
     if (problems.length === obj.length) return undefined;