CiviCases can not be found when they have no activities

When a case is created you IMMEDIATELY HAVE TO assign an activity, because otherwise the Case can never be found again. Not in Advanced Search, not in the Cases Dashboard and not in the Cases Tab of the client.

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When I change
civicrm/CRM/Case/BAO/Query.php
line 463
$from .= " INNER JOIN civicrm_case_activity ON civicrm_case_activity.case_id = civicrm_case.id ";
$from .= " INNER JOIN civicrm_activity case_activity ON ( civicrm_case_activity.activity_id = case_activity.id
AND case_activity.is_current_revision = 1 )";
to
$from .= " $side civicrm_case_activity ON civicrm_case_activity.case_id = civicrm_case.id ";
$from .= " $side civicrm_activity case_activity ON ( civicrm_case_activity.activity_id = case_activity.id
AND case_activity.is_current_revision = 1 )";

All searches seem to work, but I have no overview of other negative effects of this change.