Test: a damaged list in metadata.json, and records that stop decrypting

A metadata.json whose list of what the refresh could not decrypt is
damaged must load as an empty store. A backup after an album and a
file's copy stop decrypting removes the album's folder and JSON and the
file's link in its album, and keeps the originals.

Model: opus-5-5

test/library/store.test.ts

@@ -172,6 +172,29 @@ describe("MetadataStore", () => {
         expect(store.listCollections()).toEqual([]);
     });
 
+    it("loads an empty store when the list of what the refresh could not decrypt is damaged", async () => {
+        // A backup reads that list on every run, so a damaged one that loaded
+        // would fail every backup until the cache was deleted. A string is
+        // damaged too, though JavaScript can loop over its characters.
+        mkdirSync(join(dir, "cache"), { recursive: true });
+        for (const undecryptable of [{}, "not a list", [1]]) {
+            writeFileSync(
+                path,
+                JSON.stringify({
+                    schemaVersion: METADATA_SCHEMA_VERSION,
+                    userID: 42,
+                    collectionsSinceTime: 0,
+                    collections: [],
+                    files: [],
+                    undecryptable,
+                }),
+            );
+            const store = await MetadataStore.load(path);
+            expect(store.userID).toBe(0);
+            expect(store.listUndecryptable()).toEqual([]);
+        }
+    });
+
     it("creates the directory 0700 and the file 0600", async () => {
         const store = await MetadataStore.load(path);
         store.putCollection(sampleCollection());