Possible meanings are 1) someone else found that person in the act. Alternate translation: "if someone is discovered in an act of sin" or 2) that person committed the sin without intending to do evil. Alternate translation: "if someone gave in and sinned"
These words treat the Galatians as though they are all one person to emphasize that he is talking to each of them. Alternate translation: "Be concerned about yourselves" or "I say to each one of you, 'Be concerned about yourself'" (See: [[rc://en/ta/man/translate/figs-you]])
This can be stated in active form. Alternate translation: "so that nothing will tempt you also to sin" (See: [[rc://en/ta/man/translate/figs-activepassive]])