[fuzz] return valid radio transmit buffer (#3549)
[fuzz] return valid radio transmit buffer (#3549)


chshu/openthread,lanyuwen/openthread,chshu/openthread,abtink/openthread,lanyuwen/openthread,turon/openthread,lanyuwen/openthread,openthread/openthread,lanyuwen/openthread,librasungirl/openthread,openthread/openthread,librasungirl/openthread,librasungirl/openthread,bukepo/openthread,openthread/openthread,chshu/openthread,bukepo/openthread,lanyuwen/openthread,openthread/openthread,jwhui/openthread,chshu/openthread,jwhui/openthread,chshu/openthread,chshu/openthread,turon/openthread,srickardti/openthread,abtink/openthread,librasungirl/openthread,lanyuwen/openthread,srickardti/openthread,abtink/openthread,turon/openthread,jwhui/openthread,jwhui/openthread,bukepo/openthread,bukepo/openthread,abtink/openthread,srickardti/openthread,turon/openthread,srickardti/openthread