ObjectController: hard exit after REST API response

fixes #1314

doc/82-Changelog.md

@@ -25,6 +25,9 @@ master (will be 1.6.0)
 ### Configuration rendering
 * FIX: Fix compatibility with Icinga v2.6, got broken with v1.5.0 (#1614)
 
+### REST API
+* FIX: No more invalid JSON in some special circumstances (#1314)
+
 1.5.1
 -----
 ### Fixed issues

library/Director/Web/Controller/ObjectController.php

@@ -59,6 +59,12 @@ abstract class ObjectController extends ActionController
                 $handler->setObject($this->object);
             }
             $handler->dispatch();
+            // Hint: also here, hard exit. There is too much magic going on.
+            // Letting this bubble up smoothly would be "correct", but proved
+            // to be too fragile. Web 2, all kinds of pre/postDispatch magic,
+            // different view renderers - hard exit is the only safe bet right
+            // now.
+            exit;
         } else {
             $this->eventuallyLoadObject();
             if ($this->getRequest()->getActionName() === 'add') {