nextpnr-ice40 - blinky.json won't open using gui File->Open JSON

[etheory]

Dear YosysHQ,

When I try and load the .json file at:
nextpnr\ice40\examples\blinky (i.e. blinky.json, created by following: https://github.com/YosysHQ/nextpnr#readme) from the nextpnr-ice40 gui, using: "File->Open JSON"
I get the following error message:

NOTE: this only seems to occur is you opened the tool from the command-line with an existing .json file.
Having said that, it still feels like a legit bug.