title: UIGraphicsGetCurrentContext() returns nil -what now?
body: <p>I'm writing an iOS application and integrated <a href="https://github.com/fulldecent/FDWaveformView" rel="nofollow noreferrer">FDWaveformView</a> 2.0.0 via CocoaPods.
  Sometimes UIGraphicsGetCurrentContext() returns nil and I get the "FDWaveformView failed to get graphics context" log message. </p>
  
  <pre><code>   guard let context = UIGraphicsGetCurrentContext() else {
          NSLog("FDWaveformView failed to get graphics context")
          return
      }
  </code></pre>
  
  <p>Does anyone know how to solve this issue?</p>