D3 Examples - d3.layout.stack() error with differing array lengths

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<!DOCTYPE html>
  <head>
    <meta charset="utf-8">
    <script src="https://cdnjs.cloudflare.com/ajax/libs/d3/3.5.5/d3.min.js"></script>
    <style>
      
      body { 
        margin:0;
        box-sizing: border-box;
        width: 100vw;
        height: 100vh;
        position: relative;
      }
      
      svg { 
        width: 100%; 
        height: 100%; 
      }
      
      .original-example, .revised-example {
        position: absolute;
        right: 40px;
        width: 250px;
      }
      
      .original-example {
        top: 0;
      }
      
      .revised-example {
        top: 270px;
      }
      
      pre {
        background-color: #d0d0d0;
        padding: 5px;
      }
      
      .warning {
        visibility: hidden;
        color: red;
        position: absolute;
        top: 40%;
        left: 13%;
        font-weight: bold;
        
      }
      
      input[type="radio"]:last-of-type {
        margin-left: 4em;
      }
      
      .axis path, .axis line {
        fill: none;
        stroke: #000;
        stroke-width: 2px;
        shape-rendering: crispEdges;
      }
      
      .minus {
        position: absolute;
        right: 265px;
        top: 295px;
        font-size: 55px;
        color: red;
      }
      
    </style>
  </head>
​
  <body>
    
    <div class="original-example">
        <input type="radio" class="original">Original Data
        <pre></pre>
    </div>
    
    <div class="revised-example">
        <input type="radio" class="revised">Remove Object from Array
        <pre></pre>
    </div>
    
    <p class="minus">-</p>
    
    <p class="warning">Uncaught TypeError: Cannot read property '1' of undefined</p>
    
    <figure class="svg-container"></figure>
    
    <script>
      var data = [
        {
          key: 'Thing1',
          values: [
            {
              year: 1990,
              amount: 5
            },
            {
              year: 1991,
              amount: 6
            },
            {
              year: 1992,
              type: 'fries',
              amount: 3
            }
          ]
        },
        {
          key: 'Thing2',
          values: [
            {
              year: 1990,
              amount: 2
            },
            {
              year: 1991,
              amount: 1
            },
            {
              year: 1992,
              amount: 1
            }
          ]
        },
        {
          key: 'Thing3',
          values: [
            {
              year: 1990,
              amount: 4
            },
            {
              year: 1991,
              amount: 2
            },
            {
              year: 1992,
              amount: 6
            }
          ]
        }
      ];
      
      var layers;
      
      // display data examples in DOM
      d3.select('.original-example pre').html(function() {
        return JSON.stringify(data[2]['values'], null, 4);
      });
      
      d3.select('.revised-example pre').html(function() {
        var copy = data[2]['values'].slice(0);
        copy.splice(1, 1);
        return JSON.stringify(copy, null, 4);
      });
      
      //initialize original data
      d3.select('.original-example input').node().checked = true;
      
      var colors = ["#045A8D", "#2B8CBE", "#74A9CF"];
      
      var width = 500;
            var height = 400;
      
      var margin = {top: 10, right: 10, bottom: 0, left: 50};
      var svg = d3.select('.svg-container').append('svg')
        .attr('width', width + margin.left + margin.right)
        .attr('height', height + margin.top + margin.bottom);
      
      var g = svg.append('g')
        .attr('transform', 'translate(' + margin.left + ',' + margin.top + ')');
      
      var x = d3.scale.linear().domain([1990, 1992]).range([0, width]);
            var y = d3.scale.linear().domain([0, 20]).range([height, 0]);
            var z = d3.scale.ordinal().domain([0,2]).range(colors);
​
            var xAxis = d3.svg.axis().orient('bottom').scale(x)
        .tickValues([1990, 1991, 1992])
        .tickFormat(d3.format(".0f"));
      
            var yAxis = d3.svg.axis().orient('left').scale(y);
​
            var stack = d3.layout.stack()
        .offset("silhouette")
        .values(function(d) { return d.values; })
        .x(function(d) { return +d.year; })
        .y(function(d) { return +d.amount; });
​
            var area = d3.svg.area()
        .interpolate("cardinal")
        .x(function(d) { return x(d.year); })
        .y0(function(d) { return y(d.y0); })
        .y1(function(d) { return y(d.y0 + d.y); });
      
      layers = stack(data);
      
      g.selectAll('.layer')
        .data(layers)
        .enter().append('path')
        .classed('layer', true)
        .attr('d', function(d) { return area(d.values); })
        .style('fill', function(d, i) { return z(i); });
      
      g.append('text')
        .attr('transform', 'translate(350, 250) rotate(-10)')
        .text('Example Data Set ➜')
        .attr('fill', 'white')
      
​
      // radio button clicks
      d3.select('.original').on('click', function() {
        d3.select('.revised').node().checked = false;
        d3.select('.svg-container').style('visibility', 'visible');
        d3.select('.warning').style('visibility', 'hidden');
      });
​
      d3.select('.revised').on('click', function() {
        d3.select('.original').node().checked = false;
        d3.select('.svg-container').style('visibility', 'hidden');
        d3.select('.warning').style('visibility', 'visible');
      });
      
      // x axis
      g.append('g')
                .attr('class', 'x axis')
                .attr('transform', 'translate(0,'+ height + ')')
        .call(xAxis);
​
      // y axis
            g.append('g')
                .attr('class', 'y axis')
        .call(yAxis);
      
      
      
    </script>
  </body>
  
    