[AIBob]

if (counter<60)
{
arm = 0; 
}
tracker = counter;
else if (counter<tracker+32)
{
arm = 127; 
l_motor=r_motor=191; 
}
tracker = counter;
else if(counter < tracker + 55)
{
l_motor=r_motor=127; 
arm = 255; 
}

You have it being set between the else ifs.
there is not if that the else is attached to.
This is what is giving you the error, not the variable setting itself, just the placement of the setting.

Also note: you are setting tracker to counter before you check if it less than counter.