cannot call set current time on videojs object without offset loaded

[DanielWare]

Description

When videojs-offset is loaded but not used, it breaks the functionality of currentTime in videojs

Steps to reproduce

HTML

<video id="videojs-player1" src="//vjs.zencdn.net/v/oceans.webm" class="video-js vjs-default-skin" controls style="width:400px; height:400px;" ></video>    
<video id="videojs-player2" src="//vjs.zencdn.net/v/oceans.webm" class="video-js vjs-default-skin" controls style="width:400px; height:400px;" ></video>    
<video id="videojs-player3" src="//vjs.zencdn.net/v/oceans.webm" class="video-js vjs-default-skin" controls style="width:400px; height:400px;" ></video>    

JS

var player1 = videojs('videojs-player1');
var player2 = videojs('videojs-player2');
var player3 = videojs('videojs-player3');  
player2.offset({
  start: 10,
  end: 35,
  restart_beginning: false
});
![videojs-offset-currenttime-bug](https://user-images.githubusercontent.com/8892307/52073870-30540400-254e-11e9-8f02-52eecd0f5e75.png)
player3.currentTime(10);

Results

Expected

All 3 video progress bars update

Actual

Video1 progress bar not updating Video2 progress bar updates Video3 progress bar not updating

Error output

"VIDEOJS: TypeError: Failed to set the 'currentTime' property on 'HTMLMediaElement': The provided double value is non-finite."