firmware: Watchdog timeout when trying to download during measurement

Trying to download measurement data during a running measurement triggers the watchdog.

Configure the device, e.g. with

frame 0: dev 13 @ 2417 MHz
frame 1: dev 14 @ 2417 MHz

start a measurement and afterwards try to download measurement data by using

rss2i -a download ...

The device reboots, the red error LED gets enabled and the following message is printed via the debug port:

[0x14 0x0001/0x0001] A watchdog timeout caused the last reset.