Back out "Permit insertion into an empty IRList" (D19410556)
Back out "Permit insertion into an empty IRList" (D19410556)

Summary:
Original commit changeset: 2063bb61d6da

This caused many test failures around the class-preloader.

Reviewed By: adicatana

Differential Revision: D19471964

fbshipit-source-id: d6123996d124548dab2cae67454e37c0296d373f

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