mod_blocklist: Fix fix signal for letting stanzas pass
Returning nothing/nil lets stanzas pass, returning anything else blocks
local xpcall = xpcall;
if select(2, xpcall(function (x) return x end, function () end, "test")) ~= "test" then
xpcall = require"prosody.util.compat".xpcall;
end
return {
xpcall = xpcall;
};