[bugfix] Don't error when populating MovedTo if account not found (#2741)

* [bugfix] Don't error when populating MovedTo if account not found

* test the thing

internal/db/bundb/account.go

@@ -305,12 +305,13 @@ func (a *accountDB) PopulateAccount(ctx context.Context, account *gtsmodel.Accou
 	}
 
 	if account.MovedTo == nil && account.MovedToURI != "" {
-		// Account movedTo is not set, fetch from database.
+		// Account movedTo is not set, try to fetch from database,
+		// but only error on real errors since this field is optional.
 		account.MovedTo, err = a.state.DB.GetAccountByURI(
 			gtscontext.SetBarebones(ctx),
 			account.MovedToURI,
 		)
-		if err != nil {
+		if err != nil && !errors.Is(err, db.ErrNoEntries) {
 			errs.Appendf("error populating moved to account: %w", err)
 		}
 	}

internal/db/bundb/account_test.go

@@ -482,6 +482,17 @@ func (suite *AccountTestSuite) TestCountAccountPinnedNothingPinned() {
 	suite.Equal(pinned, 0) // This account has nothing pinned.
 }
 
+func (suite *AccountTestSuite) TestPopulateAccountWithUnknownMovedToURI() {
+	testAccount := &gtsmodel.Account{}
+	*testAccount = *suite.testAccounts["local_account_1"]
+
+	// Set test account MovedToURI to something we don't have in the database.
+	// We should not get an error when populating.
+	testAccount.MovedToURI = "https://unknown-instance.example.org/users/someone_we_dont_know"
+	err := suite.db.PopulateAccount(context.Background(), testAccount)
+	suite.NoError(err)
+}
+
 func TestAccountTestSuite(t *testing.T) {
 	suite.Run(t, new(AccountTestSuite))
 }