I have architectural shingles on my roof and one is broken. The "tooth" like section of the top layer ripped horizontally across. The bottom layer of the shingle is intact and not cracked or broken. Even if water gets under it it would obviously just run along the bottom layer so is any repair needed? Should I add sealant to attach it to the bottom layer? Should I replace the whole shingle? If I add sealant should it be just tacked by the corners or a whole horizontal bead? I only ask because it don't want to accidentally trap water anywhere. Thanks in advance for any advice.