mavlink: check index for out-of-bounds
mavlink: check index for out-of-bounds

If a MAP_RC_PARAM message is sent with an index > 2, this would lead
to undefined behaviour or a segfault/hardfault.

krbeverx/Firmware,acfloria/Firmware,acfloria/Firmware,krbeverx/Firmware,acfloria/Firmware,krbeverx/Firmware,krbeverx/Firmware,acfloria/Firmware,krbeverx/Firmware,krbeverx/Firmware,acfloria/Firmware,krbeverx/Firmware,acfloria/Firmware,acfloria/Firmware