Validate PhabricatorSearchTextField value not to be an array
Summary:
PhabricatorSearchTextField.php's parent class PhabricatorSearchField.php defines an (empty) `protected function validateControlValue($value)`.
Override this function in PhabricatorSearchTextField.php by disallowing arrays (as the only data type which cannot be casted into a text value).
Closes T15714
Test Plan: Apply D25518; then manually edit the code in `ManiphestTaskSearchEngine.php` by defining an array and passing that array to the Page Size text field via `id(new PhabricatorSearchTextField())->setDefaultValue($empty_array)`, then go to `/maniphest/query/advanced/` and see the error message.
Reviewers: O1 Blessed Committers, 20after4
Reviewed By: O1 Blessed Committers, 20after4
Subscribers: 20after4, tobiaswiese, valerio.bozzolan, Matthew, Cigaryno
Maniphest Tasks: T15714
Differential Revision: https://we.phorge.it/D25519