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

src/applications/search/field/PhabricatorSearchTextField.php

@@ -11,6 +11,15 @@ final class PhabricatorSearchTextField
     return $request->getStr($key);
   }
 
+  protected function validateControlValue($value) {
+    if (!is_array($value)) {
+      return;
+    }
+    $this->addError(
+      pht('Invalid'),
+      pht('Text value for "%s" can not be parsed.', $this->getLabel()));
+  }
+
   protected function newControl() {
     return new AphrontFormTextControl();
   }