Errors thrown from Clock.onTick are not caught

[shunter]

This is a regression introduced in #1674 . If an error occurs in a listener to Clock.onTick, the error panel is not displayed.

Sandcastle to reproduce:

var viewer = new Cesium.Viewer('cesiumContainer');

    var builtInCzml = 
[
  {
    "id":"document",
    "version":"1.0"
  },
  {
    "ellipse":{
      "outlineColor":{
        "rgba":[
          123,67,0,255
        ]
      },
      "semiMajorAxis":3000,
      "semiMinorAxis":4000,
      "height":3000
    },
    "position":{
      "cartographicDegrees":[
        -117.2,32.69,3000
      ]
    }
  }
];

    var czmlDataSource = new Cesium.CzmlDataSource();
    czmlDataSource.load(builtInCzml, 'Built-in CZML');
    viewer.dataSources.add(czmlDataSource);