Anyone who's seen 'Boogie Nights' knows that cocaine really took hold and became popular in the early 1980s ('Empire Strikes Back' debuted in 1980), hence why it would show up on the set of one of the biggest movies being made during that time period. Chances are high (no pun intended) that coke was on a lot of film sets in the '80s (and is on a lot of film sets to this day), but thankfully the drug didn't negatively impact the production to the point where it would've been noticeable back then. Fisher, of course, went on to star in 'Return of the Jedi' following 'Empire Strikes Back' (now we know how she kept that bikini figure for Slave Leia, huh?), though following the 'Star Wars' films she struggled for many years with addiction, spending time in rehab centers and psychiatric hospitals.
What she didn't mention was whether anyone else on that 'Empire Strikes Back' set was rolling around in the white stuff too. Not that it matters now, but a behind-the-scenes shot of Luke, Leia and Han Solo decked out in their snow suits snorting coke next to a sliced-open Tauntaun would've not only made for a great coffee table book, but it would've also given George Lucas a heart attack.