[4.0] Set jform in API request for assigned catid (#36538)

* Set jform i API request for assigned catid

* Update libraries/src/MVC/Controller/ApiController.php

Co-authored-by: Richard Fath <richard67@users.noreply.github.com>

* Update libraries/src/MVC/Controller/ApiController.php

Co-authored-by: Phil E. Taylor <phil@phil-taylor.com>

Co-authored-by: Richard Fath <richard67@users.noreply.github.com>
Co-authored-by: Phil E. Taylor <phil@phil-taylor.com>

libraries/src/MVC/Controller/ApiController.php

@@ -451,9 +451,12 @@ protected function save($recordKey = null)
 
 		$data = $this->preprocessSaveData($data);
 
-		// TODO: Not the cleanest thing ever but it works...
+		// @todo Not the cleanest thing ever but it works...
 		Form::addFormPath(JPATH_COMPONENT_ADMINISTRATOR . '/forms');
 
+		// Needs to be set because com_fields needs the data in jform to determine the assigned catid
+		$this->input->set('jform', $data);
+
 		// Validate the posted data.
 		$form = $model->getForm($data, false);