Fix typo in KeyframeTrack.optimize()

src/animation/KeyframeTrack.js

@@ -363,7 +363,7 @@ Object.assign( KeyframeTrack.prototype, {
 
 			// remove adjacent keyframes scheduled at the same time
 
-			if ( time !== timeNext && ( i !== 1 || time !== time[ 0 ] ) ) {
+			if ( time !== timeNext && ( i !== 1 || time !== times[ 0 ] ) ) {
 
 				if ( ! smoothInterpolation ) {