Fixed a few corner cases around 'null'.

app/Http/Controllers/InputController.php

@@ -64,11 +64,16 @@ class InputController extends Controller
     public function show(Input $input) {
         $json = json_decode($input->data);
 
-        if ($json === null)
+        // Funny thing: 'null' decodes to null just as any invalid json...
+        // Another funny thing: response()->json(null) will return '{}'...
+        // (Because php can't see, whether the parameter was provided or not...)
+        if ($input->data === 'null') {
+            return response($input->data)->header('Content-Type', 'application/json');
+        }
+        else if ($json === null)
             return $input->data;
         else
             return response()->json($json);
-
     }
 
     /**