Yeah just matchsticks on their own should work to pack the hole and provide a bit of extra "bite" for the screws. Depends on whether you push them in and they disappear into a void in the door where it has been mortised too big or larger for an old latch/lock. It's the cheapest method, but not guaranteed to be successful in every case. Tighten the screws as much as you can or does this affect the operation of the latch? If you need to slacken the screws to get the latch springing back properly and then the handle is coming loose after a while, the screws could be slightly too short.