Fixes an error that shows up in IE8+ in compatibility mode.
Fixes an error that shows up in IE8+ in compatibility mode.

youprofit/knockout,ErikSchierboom/knockout,moonpyk/knockout,brianmhunt/knockout,stonegithubs/knockout,DekeYan/knockout,martijnwetering/knockout,getshuvo/knockout,mattbalmer/knuckles,ErikSchierboom/knockout,bago/knockout,Sir0xb/knockout,pianove/knockout,xeronith/knockout,gwokudasam/knockout,moonpyk/knockout,mattbalmer/knuckles,hitesh97/knockout,gwokudasam/knockout,hitesh97/knockout,getshuvo/knockout,JesseQin/knockout,xeronith/knockout,youprofit/knockout,skyh/knockout,stonegithubs/knockout,cgourlay/knockout,Sir0xb/knockout,pianove/knockout,skyh/knockout,JesseQin/knockout,bago/knockout,brianmhunt/knockout,DekeYan/knockout,martijnwetering/knockout,cgourlay/knockout