Invalid image URI generated from README.md

[jdomeij]

Hello I have 2 node-red projects that misses the images on the flows description page

https://flows.nodered.org/node/node-red-contrib-node-hue https://flows.nodered.org/node/node-red-contrib-node-lifx

They are correctly shown on the npm and github page, looking at the HTML source for the flow page I see the following URI

<img src="undefined./doc/example_ui.png" alt="UI example">