Listen up kits and cats and I'll give you the scoop.
When you clone from cuttings (or air clone), you are taking a large number of cells, and unless the cell that began that branch (unlikely, but possible) most of which are not mutated. So when you take a cutting from that plant, most of that clone isn't mutated either. There is a small possibility that your clone isn't an exact match to the original, and that possibility goes up slightly over time, since that precise set of genes has longer exposure to environmental mutagens than may induce mutation.
So for all practical purposes, a clone is an exact copy no matter how often copied unless you get unlucky, and if the universe is out to get you that much it's going to do it no matter what so don't worry about it.
The other methods of tissue cloning use a small group of cells to make a large number of clones, so any mutated cells that are used in the inital sample become full fledged mutants.