Minor bugs

[richardbaronpenman]

Hello,

this is a really handy project - thanks for releasing.

A few minor bugs I found:

• can not include links in decisions (works for process and finish types though)
• if the yes/no nodes for a decision are undefined then no problem, however if the "next" node is undefined then the flowchart does not render fully
• if change height / width of a component then arrows become messy