M3TRO1212

I was going to get MinecraftUniverse's Hexxit map and I downloaded it and put in in the saves folder in .technic and I started the technic launcher and I started hexxit. It started fine then I clicked on the save and when it was downloading the terrain a screen popped up and says ''Forge Mod Loader has found ID mismatches Complete details are in the log file ID 31999 from Mod PetBat is missing do you wish to continue loading?'' if I click yes or no the game will crash do I have to install the pet bat mod? If anyone can help that would be amazing! Thanks.