`nullref` might be changed unexpectedly while require rapidjson multi times in different lua states. about lua-rapidjson

[gottfriedleibniz]

Here's an example of rapidjson.null failing with the new commit:

json = require'rapidjson'
example = {
    1, 2, json.null(), 3
}

print("Main", json.encode(example))

-- false   test.lua:8: value type : function
print(coroutine.resume(coroutine.create(function()
    print("Coroutine", json.encode(example))
end)))

Also, if you analyze the above script with Valgrind you will notice that there's a memory leak (see http://lua-users.org/wiki/ErrorHandlingBetweenLuaAndCplusplus).

[xpol]

Should be fixed on the master with 860c728.
Will fix GitHub actions later and make a new release.

[xpol]

Should be fixed in v0.7.0 also published to luarocks.

Note, now the type of rapidjson.null is not a function any. If you have ever called, remove the () from now on.