[Change] the check in timer.lua to IsValid
[Change] the check in timer.lua to IsValid

As suggested by Divran in 930a1250e0e1bf7fc1a824004e99d86ce0ab252f

Jazzelhawk/Starfall,Ingenious-Gaming/Starfall,Xandaros/Starfall,INPStarfall/Starfall,Ingenious-Gaming/Starfall,Jazzelhawk/Starfall,INPStarfall/Starfall,Xandaros/Starfall