What should I do if my ablution is suddenly invalidated during Friday prayer, given that I go early to attain the reward mentioned in the noble Hadith: "Whoever washes, and bathes, and goes early, and comes early, and draws near, and listens attentively, and keeps silent, will have what is between that Friday and the next forgiven, and an additional three days; and whoever touches pebbles has engaged in idle talk," and going to renew my ablution would cause me to lose my place in the first row and force me to pray at the back of the mosque?

If you are certain that your ablution has been invalidated, then you must perform ablution. It is preferable that you return to your place if possible, for the Prophet, peace and blessings be upon him, said: "Whoever stands up from his sitting place and then returns to it, he has a greater right to it." If you are unable to return to your place due to crowding, then pray wherever it is easy for you. You will still receive the reward of the first row and of coming early through your sincere intention, for the Prophet, peace and blessings be upon him, said: "Indeed, there are people in Medina behind us; we did not traverse any mountain path or valley but they were with us in it, detained by their excuse." Do not leave the sermon or the prayer unless you are absolutely certain that your ablution has been invalidated, and beware of the whisperings of Satan.