Fixes my mess-up with plants exuding gasses

Created by: Kammerjunk

I'm not good at this I changed it to check for both if the list exists and if the list has a length (because not checking for the latter makes it trigger even when the list is empty and I think not checking for both returns a runtime in the unlikely event there IS no exude_gasses var?). I don't know why it says "2 additions and 0 deletions" because those two lines exist already. Shouldn't it say "1 addition and 1 deletion"? This'll fix plants going "ADMIN LOG: Admin (kammerjunk) has planted a packet exuding nothing. (JMP)" and keep them going "ADMIN LOG: Admin (kammerjunk) has planted a packet exuding plasma and oxygen. (JMP)"