Merge pull request phaserjs#1710 from hardalias/bugfix/tween_dividebyzero

Fixes neverending tween when duration set to zero (caused by division with zero)

Author: photonstorm

src/tween/Tween.js

@@ -183,7 +183,7 @@ Phaser.Tween.prototype = {
     */
     to: function (properties, duration, ease, autoStart, delay, repeat, yoyo) {
 
-        if (typeof duration === 'undefined') { duration = 1000; }
+        if (typeof duration === 'undefined' || duration <= 0) { duration = 1000; }
         if (typeof ease === 'undefined') { ease = Phaser.Easing.Default; }
         if (typeof autoStart === 'undefined') { autoStart = false; }
         if (typeof delay === 'undefined') { delay = 0; }