Just correct it by pen. Lots of guys who made mistakes, when called FPSC, were told to correct it by pen. So, write about your attempt's year, roll number and status by pen.
PS: Also call FPSC just to satisfy yourself, whereas, I am sure they would tell you to correct it by pen.

Now, look at this rule;
''The hard copy of the online form should have the same
entries as made in the online form submitted to FPSC, and
any variation shall cause rejection of candidature.''
This rule is worrying me too. Since I have submitted my form prior to the announcement of result, so, I left the previous attempts section empty. Then in the printed form I wrote particulars of my attempt with ''result awaiting'' by pen. This created a difference between my online and printed form and the aforementioned rule!!!!
I will call them and they will not attend it.

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"Whomever Allah guides, no one can misguide, and whomever Allah misguides, no one can guide." Al-Qura'an.