Make sure you are only including positions that help you. Common mistake I see is including tiny 2-3 month long positions, without considering whether including them is additive or not. It's often not.
I'd rather see "waiting tables" rather than nothing
But why? Maybe the person used that time to study technologies, to update her skill set. Maybe she used that time to relax and get a long deserved vacation. (Or a myriad other possibilities.) What is wrong with that?
If somebody set aside 3 months to study something they should write that. Otherwise it loos like they've been unemployed, in jail or something they rather don't want to talk about.
Also I read it as multiple 3 months gaps. I might have misread though.
Personally I'd consider undescribed gaps of 3 months in between the interesting projects unusual.
In fact I'd rather see "waiting tables" rather than nothing.