Enabled session in 404 responses

Fixes #634

app/Exceptions/Handler.php

@@ -4,11 +4,14 @@ namespace BookStack\Exceptions;
 
 use Exception;
 use Illuminate\Auth\AuthenticationException;
+use Illuminate\Http\Request;
+use Illuminate\Pipeline\Pipeline;
 use Illuminate\Validation\ValidationException;
 use Illuminate\Database\Eloquent\ModelNotFoundException;
 use Symfony\Component\HttpKernel\Exception\HttpException;
 use Illuminate\Foundation\Exceptions\Handler as ExceptionHandler;
 use Illuminate\Auth\Access\AuthorizationException;
+use Symfony\Component\HttpKernel\Exception\NotFoundHttpException;
 
 class Handler extends ExceptionHandler
 {
@@ -60,9 +63,32 @@ class Handler extends ExceptionHandler
             return response()->view('errors/' . $code, ['message' => $message], $code);
         }
 
+        // Handle 404 errors with a loaded session to enable showing user-specific information
+        if ($this->isExceptionType($e, NotFoundHttpException::class)) {
+            return $this->loadErrorMiddleware($request, function ($request) use ($e) {
+                $message = $e->getMessage() ?: trans('errors.404_page_not_found');
+                return response()->view('errors/404', ['message' => $message], 404);
+            });
+        }
+
         return parent::render($request, $e);
     }
 
+    /**
+     * Load the middleware required to show state/session-enabled error pages.
+     * @param Request $request
+     * @param $callback
+     * @return mixed
+     */
+    protected function loadErrorMiddleware(Request $request, $callback)
+    {
+        $middleware = (\Route::getMiddlewareGroups()['web_errors']);
+        return (new Pipeline($this->container))
+            ->send($request)
+            ->through($middleware)
+            ->then($callback);
+    }
+
     /**
      * Check the exception chain to compare against the original exception type.
      * @param Exception $e