`if()` requires double parentheses when dividing

[MartijnCuppens]

Follow-up on #3615:

For Less v4:

Input	Expected	Result	Ok?
value: if(false, 0, 6 / 3);	value: 6 / 3;	value: 6 / 3;	👍
value: if(false, 0, (6 / 3));	value: 2;	value: 6 / 3;	👎
value: if(false, 0, ((6 / 3)));	value: 2;	value: 2;.	👍