fix: don't emit Hooks when hookpaths are empty

[miaulalala]

• Resolves: [Bug]: File Ownership Transfer through Web UI fails with TypeError: OC\Files\Node\HookConnector::getNodeForPath(): Argument #1 ($path) must be of type string, null given #38889

Summary

Fixes Transferring ownership issues when not using OCC command but GUI.

Checklist

• Code is properly formatted
• Sign-off message is added to all commits
• Tests (unit, integration, api and/or acceptance) are included
• Screenshots before/after for front-end changes
• Documentation (manuals or wiki) has been updated or is not required
• Backports requested where applicable (ex: critical bugfixes)

[miaulalala]

/backport to stable27

[miaulalala]

/backport to stable26

[miaulalala]

/backport to stable25

[miaulalala]

Drone failure unrelated:

Scenario: Browse disabled apps # /drone/src/tests/acceptance/features/apps.feature:26
--
143 | Given I act as Jane # ActorContext::iActAs()
144 | And I am logged in as the admin # LoginPageContext::iAmLoggedInAsTheAdmin()
145 | And I open the Apps management # SettingsMenuContext::iOpenTheAppsManagement()
146 | When I open the "Disabled apps" section # AppNavigationContext::iOpenTheSection()
147 | Then I see that the current section is "Disabled apps" # AppNavigationContext::iSeeThatTheCurrentSectionIs()
148 | And I see that there are only disabled apps # AppsManagementContext::iSeeThatThereAreOnlyDisabledApps()
149 | Found enabled apps

┌─ @BeforeScenario # ActorContext::initializeActors()
--
209 | │
210 | ╳ Could not open connection: unknown error: Chrome failed to start: exited abnormally.
211 | ╳ (unknown error: DevToolsActivePort file doesn't exist)
212 | ╳ (The process started from chrome location /usr/bin/google-chrome is no longer running, so ChromeDriver is assuming that Chrome has crashed.)
213 | ╳ (Driver info: chromedriver=90.0.4430.24 (4c6d850f087da467d926e8eddb76550aed655991-refs/branch-heads/4430@{#429}),platform=Linux 5.4.0-126-generic x86_64) (WARNING: The server did not provide any stacktrace information)
214 | ╳ Command duration or timeout: 364 milliseconds
215 | ╳ Build info: version: '3.141.59', revision: 'e82be7d358', time: '2018-11-14T08:25:53'
216 | ╳ System info: host: '970305e75525', ip: '172.23.0.2', os.name: 'Linux', os.arch: 'amd64', os.version: '5.4.0-126-generic', java.version: '1.8.0_282'
217 | ╳ Driver info: driver.version: unknown (Behat\Mink\Exception\DriverException)
218 | │

[max-nextcloud]

Tested locally and worked... as soon as i had the notifcations app installed ☺️