```
for(var/mob/M in player_list)
//works like....
for(var/m in player_list)
   var/mob/M = m
   if(!istype(M)) continue

istype(null,/anypath) will always return false as null has no type. Same with strings and numbers
Any non-true value will return false.
So we do not need to check if it's a true value with if(M)