fix: very old .etherpad imports could break import due to lack of aut… (#7473)

* fix: very old .etherpad imports could break import due to lack of author metadata, allow this now

* test: add regression tests for old .etherpad import without author

Tests that importing an old .etherpad export (circa 2014) where
revision records lack meta.author succeeds without error, and that
getRevisionAuthor returns '' for such revisions.

Covers the fix for #6785.

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

---------

Co-authored-by: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

src/node/db/Pad.ts

@@ -173,7 +173,7 @@ class Pad {
 
   async getRevisionAuthor(revNum: number) {
     // @ts-ignore
-    return await this.db.getSub(`pad:${this.id}:revs:${revNum}`, ['meta', 'author']);
+    return await this.db.getSub(`pad:${this.id}:revs:${revNum}`, ['meta', 'author']) ?? '';
   }
 
   async getRevisionDate(revNum: number) {

src/tests/backend/specs/ImportEtherpad.ts

@@ -171,6 +171,49 @@ describe(__filename, function () {
     }
   });
 
+  // Regression test for https://github.com/ether/etherpad-lite/issues/6785
+  describe('old .etherpad imports without author metadata', function () {
+    // Old exports (circa 2014) have revisions where meta.author is missing entirely
+    const makeOldExportNoAuthor = () => ({
+      'pad:testing': {
+        atext: {
+          text: 'foo\n',
+          attribs: '|1+4',
+        },
+        pool: {
+          numToAttrib: {},
+          nextNum: 0,
+        },
+        head: 0,
+        savedRevisions: [],
+      },
+      // Revision 0 has no meta.author — this is how very old etherpads exported
+      'pad:testing:revs:0': {
+        changeset: 'Z:1>3+3$foo',
+        meta: {
+          timestamp: 1273769875976,
+          atext: {
+            text: 'foo\n',
+            attribs: '|1+4',
+          },
+        },
+      },
+    });
+
+    it('imports without error when revision lacks meta.author', async function () {
+      await importEtherpad.setPadRaw(padId, JSON.stringify(makeOldExportNoAuthor()));
+      const pad = await padManager.getPad(padId);
+      assert.equal(pad.text(), 'foo\n');
+      assert.equal(pad.head, 0);
+    });
+
+    it('getRevisionAuthor returns empty string for missing author', async function () {
+      await importEtherpad.setPadRaw(padId, JSON.stringify(makeOldExportNoAuthor()));
+      const pad = await padManager.getPad(padId);
+      assert.equal(await pad.getRevisionAuthor(0), '');
+    });
+  });
+
   describe('exportEtherpadAdditionalContent', function () {
     let hookBackup: Function;