Fixed a ConcurrentModificationException (thanks stress-testers!)
Fixed a ConcurrentModificationException (thanks stress-testers!)

GlowstonePlusPlus/GlowstonePlusPlus,Tonodus/GlowSponge,jimmikaelkael/GlowstonePlusPlus,Tonodus/WaterGleam,jimmikaelkael/GlowstonePlusPlus,karlthepagan/Glowstone,kukrimate/Glowstone,GlowstoneMC/GlowstonePlusPlus,GreenBeard/GlowstonePlusPlus,Tonodus/WaterGleam,Tonodus/WaterGleam,kukrimate/Glowstone,GreenBeard/GlowstonePlusPlus,Postremus/GlowstonePlusPlus,GlowstoneMC/GlowstonePlusPlus,BlazePowered/Blaze-Server,Postremus/GlowstonePlusPlus,GlowstonePlusPlus/GlowstonePlusPlus,BlazePowered/Blaze-Server,kukrimate/Glowstone,jimmikaelkael/GlowstonePlusPlus,karlthepagan/Glowstone,keke142/GlowstonePlusPlus,jimmikaelkael/GlowstonePlusPlus,LukBukkit/GlowstonePlusPlus,LukBukkit/GlowstonePlusPlus,LukBukkit/GlowstonePlusPlus,Tonodus/GlowSponge,karlthepagan/Glowstone,GreenBeard/GlowstonePlusPlus,Tonodus/GlowSponge,GlowstoneMC/GlowstonePlusPlus,kukrimate/Glowstone,Postremus/GlowstonePlusPlus,Tonodus/WaterGleam,LukBukkit/GlowstonePlusPlus,Postremus/GlowstonePlusPlus,keke142/GlowstonePlusPlus,keke142/GlowstonePlusPlus,GreenBeard/GlowstonePlusPlus,Tonodus/GlowSponge,BlazePowered/Blaze-Server,GlowstonePlusPlus/GlowstonePlusPlus,GlowstoneMC/GlowstonePlusPlus,GlowstonePlusPlus/GlowstonePlusPlus,keke142/GlowstonePlusPlus,BlazePowered/Blaze-Server