[Dashboard] Custom Graph Dissappears With Payload

Hello everyone!

I've been using Node-Red for a while and now I'm facing a problem when I want to use custom HTML on Dashboard's template node.

When I put the payload as {{msg.payload.data}} into my graph's data input, the graph disappears. I've checked the Chrome's console output and saw a message saying:
Refused to apply style from 'https://efesaniot.eu-gb.mybluemix.net/ui/dizayn.css' because its MIME type ('text/html') is not a supported stylesheet MIME type, and strict MIME checking is enabled.

When I replace the payload format with number, everything is okay. Is there a way to forward just the number to graph input without directly using {{msg.payload}}?

Any help would be very much appreaciated. Thank you very much!