fix TVMRetValue move constructor not clear old value (#144)

* fix TVMRetValue move constructor not clear old value lead to repeat delete

* fix

include/tvm/runtime/packed_func.h

@@ -318,6 +318,8 @@ class TVMRetValue : public TVMPODValue_ {
    */
   TVMRetValue(TVMRetValue&& other)
       : TVMPODValue_(other.value_, other.type_code_) {
+    other.value_.v_handle = nullptr;
+    other.type_code_ = kNull;
   }
   /*! \brief destructor */
   ~TVMRetValue() {