Merge branch 'depthwise-bug' into 'master'

Fix op type judge bug in simple net.

See merge request !64

mace/core/net.cc

@@ -23,7 +23,7 @@ SimpleNet::SimpleNet(const std::shared_ptr<const NetDef>& net_def,
     std::unique_ptr<OperatorBase> op{nullptr};
     OperatorDef temp_def(operator_def);
     op = CreateOperator(temp_def, ws, type);
-    if (!op) {
+    if (op) {
       operators_.emplace_back(std::move(op));
     }
   }