Error: Cannot read property 'key' of null

Trying to get the basic example to work with no luck.
this is what is in the body of my page:

``` html

var diagram = flowchart.parse('st=>start: Start:>http://www.google.com[blank]\n' +
'e=>end:>http://www.google.com');
diagram.drawSVG('diagram');

```

Always get the following error no matter what is inside the `parse()`.

```
TypeError: Cannot read property 'key' of null
at getDisplaySymbol (http://localhost:3000/include/plugins/flowchart/1.4.2/flowchart.js:1205:28)
at constructChart (http://localhost:3000/include/plugins/flowchart/1.4.2/flowchart.js:1236:26)
at Object.chart.drawSVG (http://localhost:3000/include/plugins/flowchart/1.4.2/flowchart.js:1269:11)
```

How do I solve this and what is the least I need to create a flowchart?

Reproduce the exact basic example from the issue, then inspect flowchart.js at getDisplaySymbol, constructChart, and chart.drawSVG, which appear in the stack trace. Confirm the minimum valid parse() input and ensure the example renders without the null-key error.

Vom Indexierungsmodell aus dem Issue-Text verfasst.