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You should learn to use the Call Hierarchy to figure out such things. I didn't know the answer but just used that to find out myself. Programmers don't usually know this stuff off the top of their head, but rather know how to use their IDE (I use Eclipse) to quickly confirm and follow code. Anyway, in this case your creative tab class should have a method called displayAllRelevantItems() or if your class doesn't have it you should @Override it from the parent class. That method takes in a list as parameter that gets populated with the items, so you could just use standard list methods for filtering or removing items.

Your mod is "MylesCannonPlusMod"? Then yes, it's your mod that's crashing. How to fix it? Stop using MCreator and learn how to properly mod.