BUG Gridfield fails when save changes filter criteria (fixes #7785)

forms/gridfield/GridFieldDetailForm.php

@@ -364,14 +364,14 @@ protected function getToplevelController() {
 
 	function doSave($data, $form) {
 		$new_record = $this->record->ID == 0;
+		$controller = Controller::curr();
 
 		try {
 			$form->saveInto($this->record);
 			$this->record->write();
 			$this->gridField->getList()->add($this->record);
 		} catch(ValidationException $e) {
 			$form->sessionMessage($e->getResult()->message(), 'bad');
-			$controller = Controller::curr();
 			$responseNegotiator = new PjaxResponseNegotiator(array(
 				'CurrentForm' => function() use(&$form) {
 					return $form->forTemplate();
@@ -398,10 +398,16 @@ function doSave($data, $form) {
 
 		if($new_record) {
 			return Controller::curr()->redirect($this->Link());
-		} else {
+		} elseif($this->gridField->getList()->byId($this->record->ID)) {
 			// Return new view, as we can't do a "virtual redirect" via the CMS Ajax
 			// to the same URL (it assumes that its content is already current, and doesn't reload)
 			return $this->edit(Controller::curr()->getRequest());
+		} else {
+			// Changes to the record properties might've excluded the record from
+			// a filtered list, so return back to the main view if it can't be found
+			$noActionURL = $controller->removeAction($data['url']);
+			$controller->getRequest()->addHeader('X-Pjax', 'Content'); 
+			return $controller->redirect($noActionURL, 302); 
 		}
 	}