Defensive fix for process.config.variables regression (v5)
Updated defensive fix (v2 PR of https://github.com/nodejs/node/pull/6110)
This is the 5.x PR, the 4.x one is here:
https://github.com/nodejs/node/pull/6114
Discussion here:
https://github.com/nodejs/node/pull/3755#issuecomment-207066246