[ts] Fixed issue with mixDuration on dip mix entry being 0. Caused NaNs when applying mixing from

spine-ts/core/src/AnimationState.ts

@@ -220,7 +220,7 @@ module spine {
 					first = true;
 					alpha = alphaDip;
 					let dipMix = timelineDipMix[i];
-					if (dipMix != null) alpha *= Math.max(0, 1 - dipMix.mixTime / dipMix.mixDuration);
+					if (dipMix != null && dipMix.mixDuration > 0) alpha *= Math.max(0, 1 - dipMix.mixTime / dipMix.mixDuration);
 					break;
 				}
 				if (timeline instanceof RotateTimeline)