AV: crashes with tileSize = nil

[dblock]

From a test that wasn't setting tileSize, still needs a proper repro within ARTiledImageView.

Thread 2 Crashed:: com.apple.CoreAnimation.render-server
0   QuartzCore                      0x0086c7ac CA::OGL::TiledImageGeometry::TiledImageGeometry(CA::Render::TiledTexture*, CA::OGL::Context&, unsigned int, CA::OGL::TextureFilter, CA::OGL::TextureFilter, float, CA::OGL::ContentsGeometry const*) + 1650
1   QuartzCore                      0x0086e4fe CA::OGL::draw_tiled_image(CA::OGL::Context&, CA::Render::TiledTexture*, CA::OGL::TextureFilter, CA::OGL::TextureFilter, float, CA::OGL::ContentsGeometry const&, bool) + 80
2   QuartzCore                      0x00831860 CA::OGL::render_contents_background(CA::OGL::Renderer&, CA::OGL::Layer const*) + 1858
3   QuartzCore                      0x00829350 CA::OGL::LayerNode::apply(float, CA::OGL::Surface**, float*) + 56
4   QuartzCore                      0x00827f10 CA::OGL::ImagingNode::render(CA::OGL::ImagingNode::RenderClosure*, unsigned int) + 480
5   QuartzCore                      0x00834d08 CA::OGL::render_layers(CA::OGL::Renderer&, CA::OGL::Layer*) + 160
6   QuartzCore                      0x008293f7 CA::OGL::LayerNode::apply(float, CA::OGL::Surface**, float*) + 223
7   QuartzCore                      0x00827f10 CA::OGL::ImagingNode::render(CA::OGL::ImagingNode::RenderClosure*, unsigned int) + 480
8   QuartzCore                      0x00834d08 CA::OGL::render_layers(CA::OGL::Renderer&, CA::OGL::Layer*) + 160
9   QuartzCore                      0x008293f7 CA::OGL::LayerNode::apply(float, CA::OGL::Surface**, float*) + 223
10  QuartzCore                      0x00827f10 CA::OGL::ImagingNode::render(CA::OGL::ImagingNode::RenderClosure*, unsigned int) + 480
11  QuartzCore                      0x00834d08 CA::OGL::render_layers(CA::OGL::Renderer&, CA::OGL::Layer*) + 160
12  QuartzCore                      0x008293f7 CA::OGL::LayerNode::apply(float, CA::OGL::Surface**, float*) + 223
13  QuartzCore                      0x00827f10 CA::OGL::ImagingNode::render(CA::OGL::ImagingNode::RenderClosure*, unsigned int) + 480
14  QuartzCore                      0x00834d08 CA::OGL::render_layers(CA::OGL::Renderer&, CA::OGL::Layer*) + 160
15  QuartzCore                      0x008293f7 CA::OGL::LayerNode::apply(float, CA::OGL::Surface**, float*) + 223
16  QuartzCore                      0x00827f10 CA::OGL::ImagingNode::render(CA::OGL::ImagingNode::RenderClosure*, unsigned int) + 480
17  QuartzCore                      0x00834d08 CA::OGL::render_layers(CA::OGL::Renderer&, CA::OGL::Layer*) + 160
18  QuartzCore                      0x008293f7 CA::OGL::LayerNode::apply(float, CA::OGL::Surface**, float*) + 223
19  QuartzCore                      0x00827f10 CA::OGL::ImagingNode::render(CA::OGL::ImagingNode::RenderClosure*, unsigned int) + 480
20  QuartzCore                      0x00834d08 CA::OGL::render_layers(CA::OGL::Renderer&, CA::OGL::Layer*) + 160
21  QuartzCore                      0x008293f7 CA::OGL::LayerNode::apply(float, CA::OGL::Surface**, float*) + 223
22  QuartzCore                      0x00827f10 CA::OGL::ImagingNode::render(CA::OGL::ImagingNode::RenderClosure*, unsigned int) + 480
23  QuartzCore                      0x00834d08 CA::OGL::render_layers(CA::OGL::Renderer&, CA::OGL::Layer*) + 160
24  QuartzCore                      0x00834ef6 CA::OGL::render_root_layers(CA::OGL::Renderer&, x_link_struct const*, CA::OGL::Gstate const&) + 352
25  QuartzCore                      0x0084aaa5 CA::OGL::Renderer::render(CA::Render::Update const*) + 583
26  QuartzCore                      0x0087c44b CA::WindowServer::Display::render_display(CA::OGL::Renderer&, CA::Render::Update*) + 363
27  QuartzCore                      0x0087fe5a CA::WindowServer::Server::render_update(CA::Render::Update*, unsigned int&) + 44
28  QuartzCore                      0x0087f8de CA::WindowServer::Server::render_for_time(double, CVTimeStamp const*) + 1786
29  QuartzCore                      0x0087f1de CA::WindowServer::Server::timer_callback(double, void*) + 34
30  QuartzCore                      0x0080e5ac CA::Render::Server::run_callbacks() + 156
31  QuartzCore                      0x0080e122 CA::Render::Server::server_thread(void*) + 155
32  QuartzCore                      0x008e0ad4 thread_fun + 29
33  libsystem_pthread.dylib         0x01a595fb _pthread_body + 144
34  libsystem_pthread.dylib         0x01a59485 _pthread_start + 130
35  libsystem_pthread.dylib         0x01a5ecf2 thread_start + 34