What is Chrome Debugger showing undefined for object created with spread (Create React App)?

I'm using Chrome 62.0.3202.94, and finding that with ES6 and Create React App and flow (removed from the segment for troubleshooting), and noticing the issue below. It seems when I set newState by spreading the state, newState shows as undefined. The code seems to execute as planned, though.

Is this a known thing, or am I doing something wrong? Elsewhere in this reducer file, I'm using Flow, should I try removing all Flow from this file, and trying again? This is the first time I've noticed this on my end.

Edit: Completely removed Flow from the file, and the issue still appears. Also tested in the latest Firefox with the same issue. Also, I noticed if I declare variables as "var" and not "let", things work more as I would expect.

Chrome Issue