The only thing I can think is that you are talking about loading the bar with less than 135 pounds, and in the absence of bumper plates.
It doesn't matter. Pulling from a slight "deficit" for a couple warmup sets isn't going to affect anything. When using the empty bar, you can kind of do a deep RDL (holding the bar at the spot on the shins where the plates would put it) if you want. Your weights will soon get heavy enough that this doesn't matter.
If you're power cleaning, and you should be, you'll need a set of bumper plates.
You can just use a stack of plates. That's what I did in the beginning.
The weights are light enough that you should be able to lower under full control, so you can make the plate land on the same spot (the hole that hangs off the bar) every time so that it won't roll off.