fix crash when None is passed to enum::operator==

Author: Wenzel Jakob

include/pybind11/pybind11.h

@@ -409,7 +409,6 @@ class cpp_function : public function {
                         }
                     }
                 }
-
                 if (kwargs_consumed == nkwargs)
                     result = it->impl(it, args_, parent);
 
@@ -937,10 +936,11 @@ template <typename Type> class enum_ : public class_<Type> {
                 ((it == entries->end()) ? std::string("???")
                                         : std::string(it->second));
         });
-        this->def("__init__", [](Type& value, int i) { value = (Type) i; });
+        this->def("__init__", [](Type& value, int i) { value = (Type)i; });
+        this->def("__init__", [](Type& value, int i) { new (&value) Type((Type) i); });
         this->def("__int__", [](Type value) { return (int) value; });
-        this->def("__eq__", [](const Type &value, Type value2) { return value == value2; });
-        this->def("__ne__", [](const Type &value, Type value2) { return value != value2; });
+        this->def("__eq__", [](const Type &value, Type *value2) { return value2 && value == *value2; });
+        this->def("__ne__", [](const Type &value, Type *value2) { return !value2 || value != *value2; });
         this->def("__hash__", [](const Type &value) { return (int) value; });
         m_entries = entries;
     }