well, first of all, there is no if loop, there's a for loop, if that is what you mean and if you're talking about if statement then the set up is this:
if (this is true then...)
{
this
}
else // if not then...
{
that
}
if you want to use the if statement then you have to use else because if the statement in the parenthesis isn't true then it has no output for if it's not true. If you simply want to leave the output for else out then you do this ( put nothing in else curly brackets).
if ( this is true then...)
{
this
}
else
{
}
continue code right here...