Fix regression in 'this' & 'try' step methods
Fix regression in 'this' & 'try' step methods

Last commit was missing `var stack = this.stateStack` in a couple
places, causing use of 'this' and 'try' to fail.

google/CodeCity,google/CodeCity,google/CodeCity,NeilFraser/CodeCity,NeilFraser/CodeCity,google/CodeCity,NeilFraser/CodeCity,NeilFraser/CodeCity