borderRadius does not work with integer (needs string with px)

[fdietze]

works:

borderRadius := "3px"

doesn't work:

borderRadius := 3

[lihaoyi]

fontSize suffers the same problem

[leonardehrenfried]

I was just bitten by this.

This results in a very hard to track down NPE in the browser. Could the error message be at at least be a little improved?