From 555eebf3f4845c8138c24ded96fcb3fa5c67787a Mon Sep 17 00:00:00 2001
From: Hein-Pieter van Braam <hp@tmm.cx>
Date: Fri, 2 Mar 2018 09:37:32 +0100
Subject: [PATCH] Don't crash when trying to add an invalid navmesh

It is possible to try to add an invalid object as a navmesh through
GDScript which results in an engine crash. This creates a debug message
that should help the user figure out what's wrong.
---
 scene/3d/navigation.cpp | 1 +
 1 file changed, 1 insertion(+)

diff --git a/scene/3d/navigation.cpp b/scene/3d/navigation.cpp
index e7ab6cde8a0..77bf7037061 100644
--- a/scene/3d/navigation.cpp
+++ b/scene/3d/navigation.cpp
@@ -35,6 +35,7 @@ void Navigation::_navmesh_link(int p_id) {
 	ERR_FAIL_COND(!navmesh_map.has(p_id));
 	NavMesh &nm = navmesh_map[p_id];
 	ERR_FAIL_COND(nm.linked);
+	ERR_FAIL_COND(nm.navmesh.is_null());
 
 	PoolVector<Vector3> vertices = nm.navmesh->get_vertices();
 	int len = vertices.size();