chg: fix an undefined behavior about memcpy
Spot by Wez Furlong. `memcpy(x, NULL, 0)` is undefined according to [1].
[1]: https://stackoverflow.com/questions/5243012
Differential Revision: https://phab.mercurial-scm.org/D3698
{
// Enforcing
"eqeqeq" : true, // true: Require triple equals (===) for comparison
"forin" : true, // true: Require filtering for..in loops with obj.hasOwnProperty()
"freeze" : true, // true: prohibits overwriting prototypes of native objects such as Array, Date etc.
"nonbsp" : true, // true: Prohibit "non-breaking whitespace" characters.
"undef" : true, // true: Require all non-global variables to be declared (prevents global leaks)
// Environments
"browser" : true // Web Browser (window, document, etc)
}