folly: ubsan: elias-fano avoid memset(nullptr)
folly: ubsan: elias-fano avoid memset(nullptr)

Reviewed By: ot

Differential Revision: D3300437

fbshipit-source-id: 7e0add5dab6dc1c891b742b4bcedea656c8284a9

mqeizi/folly,charsyam/folly,brunomorishita/folly,brunomorishita/folly,Orvid/folly,facebook/folly,brunomorishita/folly,charsyam/folly,mqeizi/folly,charsyam/folly,mqeizi/folly,floxard/folly,mqeizi/folly,rklabs/folly,rklabs/folly,rklabs/folly,facebook/folly,Orvid/folly,facebook/folly,Orvid/folly,mqeizi/folly,charsyam/folly,Orvid/folly,brunomorishita/folly,rklabs/folly,floxard/folly,facebook/folly,floxard/folly,rklabs/folly,brunomorishita/folly,facebook/folly,floxard/folly,Orvid/folly,floxard/folly