igl | metal | Fix null pointer dereference in `RenderCommandEncoder::…

…bindSamplerState()` (facebook#203)

Summary: Pull Request resolved: facebook#203

Reviewed By: dmannemela, syeh1

Differential Revision: D65838643

Pulled By: corporateshark

fbshipit-source-id: 95871d6fa0916533158455bf2ebb4aacabb2142d

src/igl/metal/RenderCommandEncoder.mm

@@ -350,13 +350,14 @@
                    "Bind target is not valid: %d",
                    bindTarget);
 
-  auto* metalSamplerState = static_cast<SamplerState*>(samplerState);
+  auto* iglSamplerState = static_cast<SamplerState*>(samplerState);
+  auto metalSamplerState = iglSamplerState ? iglSamplerState->get() : nil;
 
   if ((bindTarget & BindTarget::kVertex) != 0) {
-    [encoder_ setVertexSamplerState:metalSamplerState->get() atIndex:index];
+    [encoder_ setVertexSamplerState:metalSamplerState atIndex:index];
   }
   if ((bindTarget & BindTarget::kFragment) != 0) {
-    [encoder_ setFragmentSamplerState:metalSamplerState->get() atIndex:index];
+    [encoder_ setFragmentSamplerState:metalSamplerState atIndex:index];
   }
 }