[stable20] CalDavBackend: check if timerange is array before accessing

[backportbot-nextcloud]

backport of #23497

[faily-bot]

🤖 beep boop beep 🤖

Here are the logs for the failed build:

Status of 34337: failure

acceptance-header

• tests/acceptance/features/header.feature:33

Show full log

  Scenario: users from other groups are not seen in the contacts menu when autocompletion is restricted within the same group # /drone/src/tests/acceptance/features/header.feature:33
    Given I am logged in as the admin                                                                                         # LoginPageContext::iAmLoggedInAsTheAdmin()
    And I visit the settings page                                                                                             # SettingsMenuContext::iVisitTheSettingsPage()
    And I open the "Sharing" section of the "Administration" group                                                            # AppNavigationContext::iOpenTheSectionOf()
    And I enable restricting username autocompletion to groups                                                                # SettingsContext::iEnableRestrictingUsernameAutocompletionToGroups()
    And I see that username autocompletion is restricted to groups                                                            # SettingsContext::iSeeThatUsernameAutocompletionIsRestrictedToGroups()
    When I open the Contacts menu                                                                                             # ContactsMenuContext::iOpenTheContactsMenu()
    Then I see that the Contacts menu is shown                                                                                # ContactsMenuContext::iSeeThatTheContactsMenuIsShown()
    And I see that the contact "user0" in the Contacts menu is not shown                                                      # ContactsMenuContext::iSeeThatTheContactInTheContactsMenuIsNotShown()
      Failed asserting that true is false.
    And I see that the contact "admin" in the Contacts menu is not shown                                                      # ContactsMenuContext::iSeeThatTheContactInTheContactsMenuIsNotShown()

[MorrisJobke]

❌ Needs to wait for 20.0.2