Are there any side effects if am supposed to draw a card but have no cards to draw?
Never played the game but i'm very familiar with Star Realms.

Your question was asked here on BGG.  No official source chipped in but its seems common sense that if you are unable to do something nothing happens.  Just do as much as you can on the cards.

When I play Star Realms on the app and I want to draw cards and the draw and discard are empty then there is just no effect.