shift + 'i' should add idle workers to a selection group

[andy5995]

Normally units can be added to the selection group by using shift.

For example, if I have 3 archers selected, I can add another archer, or stickfighter, by holding down shift while clicking on it.

The 'i' key can used to select idle workers. But holding down the shift key while pressing 'i' does not add them to a selection group.