If there is a mutation because of which the triose phosphate isomerase enzyme involved in glycolysis has become non-functional. What would be number of ATP produced via aerobic respiration in this cell from one molecule of glucose?

Triose phosphate isomerase converts DHAP to PGAL. If this enzyme becomes non-functional then only DHAP will not convert to PGAL. 
Therefore, via glycolysis one molecule of pyruvic acid would be produced. This would enter link reaction and kreb cycle.
Net gain of ATP via glycolysis directly= 0 (2 produced and 2 utilized)
NADH produced via glycolysis= 1NADH= 3ATP
Link reaction, 1 NADH is produced= 3 ATP
Kreb cycle= 3 NADH, 1 ${\mathrm{FADH}}_2$, 1 ATP
3NADH= 3x3=9 ATP
1 ${\mathrm{FADH}}_2$= 2ATP
Total ATP produced=  3+3+9+2+1= 18 ATP