public void clearSpeedFactors() {
        this.speedFactors = null;
    }
Used to resolve the slow motion side effect caused by stretching actions that
doesn't have the same length.

@param speedFactors The speed factors for each child action. BlendAction will
                    interpolate factor for current frame based on blend weight
                    and will multiply it to speed.
jme3-core/src/main/java/com/jme3/anim/tween/action/BlendAction.java