rtos/riot: fix out-of-bounds writes when target is corrupted
This protects against out-of-bounds writes when the memory
of RIOT's scheduler is corrupted.
This memory can be corrupted because of:
- Programming errors
- The scheduler not yet having been initialised
- An incorrect symbol file being used during debugging.
This error can result in OpenOCD segfaulting. Valgrind was
used to find the approximate location of the error.
Change-Id: I60e7d7c245b8c4e38f4c98cb0c0347a9b5ec3177
Signed-off-by: Sebastiaan de Schaetzen <sebastiaan.de.schaetzen@gmail.com>
Reviewed-on: https://review.openocd.org/c/openocd/+/6381
Tested-by: jenkins
Reviewed-by: Antonio Borneo <borneo.antonio@gmail.com>