When a mana burst with the kindle lens is fired at the top o the block directly below a non-full block(like a torch, upside-down slab or stair, etc.), it replaces it with fire.
Maybe add an isReplaceable() check on https://github.com/Vazkii/Botania/blob/master/MODSRC/vazkii/botania/common/item/ItemLens.java#L396?