fix context lost in cast of shared primitive

h3d/prim/Instanced.hx

@@ -67,7 +67,7 @@ class Instanced extends MeshPrimitive {
 	}
 
 	override function render( engine : h3d.Engine ) {
-		if( primitive.buffer.isDisposed() )
+		if( buffer.isDisposed() )
 			setMesh(primitive);
 		engine.renderInstanced(getBuffers(engine),indexes,commands);
 	}