NC15 - Unhandled exception occ files:scan

[guzi42]

Steps to reproduce

1.occ files:scan --all
2.
3.

Expected behaviour

should complete without errors

Actual behaviour

Starting scan for user 34 out of 379 (someuser)
An unhandled exception has been thrown:
TypeError: Argument 1 passed to OC\OCS\DiscoveryService::discover() must be of the type string, null given, called in /var/www/owncloud/apps/files_sharing/lib/External/Manager.php on line 382 and defined in /var/www/owncloud/lib/private/OCS/DiscoveryService.php:65
Stack trace:
#0 /var/www/owncloud/apps/files_sharing/lib/External/Manager.php(382): OC\OCS\DiscoveryService->discover(NULL, 'FEDERATED_SHARI...')
#1 /var/www/owncloud/apps/files_sharing/lib/External/Manager.php(527): OCA\Files_Sharing\External\Manager->sendFeedbackToRemote(NULL, NULL, NULL, 'decline')
#2 /var/www/owncloud/apps/files_sharing/lib/External/Storage.php(218): OCA\Files_Sharing\External\Manager->removeShare('/files/Global E...')
#3 [internal function]: OCA\Files_Sharing\External\Storage->checkStorageAvailability()
#4 /var/www/owncloud/lib/private/Files/Storage/Wrapper/Wrapper.php(506): call_user_func_array(Array, Array)
#5 [internal function]: OC\Files\Storage\Wrapper\Wrapper->__call('checkStorageAva...', Array)
#6 /var/www/owncloud/lib/private/Files/Storage/Wrapper/Wrapper.php(506): call_user_func_array(Array, Array)
#7 /var/www/owncloud/apps/files_sharing/lib/External/Scanner.php(89): OC\Files\Storage\Wrapper\Wrapper->__call('checkStorageAva...', Array)
#8 /var/www/owncloud/apps/files_sharing/lib/External/Scanner.php(44): OCA\Files_Sharing\External\Scanner->scanAll()
#9 /var/www/owncloud/lib/private/Files/Utils/Scanner.php(245): OCA\Files_Sharing\External\Scanner->scan('', true, 3)
#10 /var/www/owncloud/apps/files/lib/Command/Scan.php(145): OC\Files\Utils\Scanner->scan('/Didiot', true, NULL)
#11 /var/www/owncloud/apps/files/lib/Command/Scan.php(201): OCA\Files\Command\Scan->scanFiles('someuser', '/someuser', Object(Symfony\Component\Console\Output\ConsoleOutput), false, true, false)
#12 /var/www/owncloud/3rdparty/symfony/console/Command/Command.php(255): OCA\Files\Command\Scan->execute(Object(Symfony\Component\Console\Input\ArgvInput), Object(Symfony\Component\Console\Output\ConsoleOutput))
#13 /var/www/owncloud/core/Command/Base.php(166): Symfony\Component\Console\Command\Command->run(Object(Symfony\Component\Console\Input\ArgvInput), Object(Symfony\Component\Console\Output\ConsoleOutput))
#14 /var/www/owncloud/3rdparty/symfony/console/Application.php(946): OC\Core\Command\Base->run(Object(Symfony\Component\Console\Input\ArgvInput), Object(Symfony\Component\Console\Output\ConsoleOutput))
#15 /var/www/owncloud/3rdparty/symfony/console/Application.php(248): Symfony\Component\Console\Application->doRunCommand(Object(OCA\Files\Command\Scan), Object(Symfony\Component\Console\Input\ArgvInput), Object(Symfony\Component\Console\Output\ConsoleOutput))
#16 /var/www/owncloud/3rdparty/symfony/console/Application.php(148): Symfony\Component\Console\Application->doRun(Object(Symfony\Component\Console\Input\ArgvInput), Object(Symfony\Component\Console\Output\ConsoleOutput))
#17 /var/www/owncloud/lib/private/Console/Application.php(213): Symfony\Component\Console\Application->run(Object(Symfony\Component\Console\Input\ArgvInput), Object(Symfony\Component\Console\Output\ConsoleOutput))
#18 /var/www/owncloud/console.php(96): OC\Console\Application->run()
#19 /var/www/owncloud/occ(11): require_once('/var/www/ownclo...')
#20 {main}root@neksowncloud:/media/ownclouddata/Didiot#

Server configuration

OS: Ubuntu 18.04.2 LTS

web server: apache2 2.4.29-1ubuntu4.5

Database: mysql-server-5.7 5.7.25-0ubuntu0.18.04.2

PHP version: 7.2

Nextcloud version: 15.0.5

Updated from an older Nextcloud/ownCloud or fresh install: from ownCloud 10 via nextcloud 12/13/14

**Where did you install Nextcloud from:**download from web installer

Signing status:

Signing status

Login as admin user into your Nextcloud and access 
http://example.com/index.php/settings/integrity/failed 
paste the results here.

No errors have been found.

</details>

**List of activated apps:**
<details>
<summary>App list</summary>

If you have access to your command line run e.g.:
sudo -u www-data php occ app:list
from within your Nextcloud installation folder

</details>

**Nextcloud configuration:**
<details>
<summary>Config report</summary>

If you have access to your command line run e.g.:
sudo -u www-data php occ config:list system
from within your Nextcloud installation folder

or

Insert your config.php content here.
Make sure to remove all sensitive content such as passwords. (e.g. database password, passwordsalt, secret, smtp password, …)

</details>

**Are you using external storage, if yes which one:** local/smb/sftp/...

**Are you using encryption:** yes/no

**Are you using an external user-backend, if yes which one:** LDAP/ActiveDirectory/Webdav/...

#### LDAP configuration (delete this part if not used)
<details>
<summary>LDAP config</summary>

With access to your command line run e.g.:
sudo -u www-data php occ ldap:show-config
from within your Nextcloud installation folder

Without access to your command line download the data/owncloud.db to your local
computer or access your SQL server remotely and run the select query:
SELECT * FROM oc_appconfig WHERE appid = 'user_ldap';

Eventually replace sensitive data as the name/IP-address of your LDAP server or groups.

</details>

### Client configuration
**Browser:**

**Operating system:**

### Logs
#### Web server error log
<details>
<summary>Web server error log</summary>

Insert your webserver log here

</details>

#### Nextcloud log (data/nextcloud.log)
<details>
<summary>Nextcloud log</summary>

Insert your Nextcloud log here

</details>

#### Browser log
<details>
<summary>Browser log</summary>

Insert your browser log here, this could for example include:

a) The javascript console log
b) The network log
c) ...

</details>

[ChristophWurst]

Fixed for 16 and requires a backport to 15: #13790 (comment)

[MorrisJobke]

fixed via #14968