Interface hangs on Copter log file, but works with identical Plane log file

When loading the `copter.bin` file the interface hangs, but the `plane.bin` works fine. The only difference between the files is one MSG message, see: [c.zip](https://github.com/user-attachments/files/17386822/c.zip)

NB1: It would be nice to be able to set the flight mode with MSG messages (in addition to the MODE messages). This to get away from the pre-defined ArduPilot modes. For example: sending MSG message "Flight Mode:flying-high" would show flying-high as flight mode in the app.

NB2: Thanks for your quick response on my previous bug report. In plotbeta it working now.

Start by reproducing the hang with the attached copter.bin file and comparing its single MSG message with the working plane.bin file. Trace the log-loading and MSG parsing path in the JavaScript interface; done means copter.bin loads without hanging while plane.bin continues to work.

Written by the indexing model from the issue text.