handle error

Author: tgymnich

lib/mtl/log_state.jl

@@ -35,5 +35,6 @@ function MTLLogState(dev::MTLDevice, descriptor::MTLLogStateDescriptor)
     err = Ref{id{NSError}}(nil)
     handle = @objc [dev::id{MTLDevice} newLogStateWithDescriptor:descriptor::id{MTLLogStateDescriptor} 
                                        error:err::Ptr{id{NSError}}]::id{MTLLogState}
+    err[] == nil || throw(NSError(err[]))
     MTLLogState(handle)
 end