message: removing case that can't happen
  there is an event added in the constructor at time 0 and the time can't be less than 0
diff: @@ -143,10 +143,7 @@ export class TickSource<TypeName extends "bpm" | "hertz"> extends ToneWithContex
  */
  getTicksAtTime(time?: Time): Ticks {
  const computedTime = this.toSeconds(time);
  - const stopEvent = this._state.getLastState("stopped", computedTime);
  - if (!stopEvent) {
  - return 0;
  - }
  + const stopEvent = this._state.getLastState("stopped", computedTime) as StateTimelineEvent;
  // this event allows forEachBetween to iterate until the current time
  const tmpEvent: StateTimelineEvent = { state: "paused", time: computedTime };
  this._state.add(tmpEvent);
  @@ -208,10 +205,7 @@ export class TickSource<TypeName extends "bpm" | "hertz"> extends ToneWithContex
  */
  getSecondsAtTime(time: Time): Seconds {
  time = this.toSeconds(time);
  - const stopEvent = this._state.getLastState("stopped", time);
  - if (!stopEvent) {
  - return 0;
  - }
  + const stopEvent = this._state.getLastState("stopped", time) as StateTimelineEvent;
  // this event allows forEachBetween to iterate until the current time
  const tmpEvent: StateTimelineEvent = { state: "paused", time };
  this._state.add(tmpEvent);
  