It really depends exactly what your problem is.
One possibility is that your chapter outline is just an initial stab at the story and as it has developed in more detail the 'blank' chapters are simply redundant now as what they were intended to cover has been dealt with already or is no longer relevant.
Alternatively it could be that you have two key scenes or situations planned and you don't know how to get from one to the other perhaps a lot of time passes without much incident or there is a dramatic change of circumstance for a particular character. If you are having trouble getting characters from pone major plot point to another this may be a symptom of some underlying problem with the story or characterization which you need to work out before rather than shoehorning in a linking chapter which doesn't work.
Another possibility is issues with pacing, for example you may have planned a particular rhythm to the story which has ended up slipping out of sync with what you have ended up writing. Say you have major events in chapters 5 and 7 and you want to use chapter 6 to separate them. Obviously a crucial consideration here is what your original logic and process was for setting out the chapters as you did in the first place. 869
Is there some underlying concept to this structure which can't easily be changed or was it just a way to get an initial structure down to get you started ?
I would also suggest that 'thinking of ideas to fill space' is not necessarily a good thing in any kind of art form. Everything which you include should be there to fill some function. For sure there may be particular problems which you need to solve but 'filling space' is rarely a good thing.
Overall some points to consider are :
* What are the logical consequences of actions and events in the previous chapter ?
* Is there any information that the reader needs to be able to make sense of the next chapter ?
* How does the blank chapter fit in with the rest of the story in terms of pacing and character development. For example an interlude between two very dramatic passages may be an opportunity for something a bit more introspective and atmospheric where characters take stock of events. This can also be an opportunity to have more atmospheric and descriptive passages which add to setting and characterization without slowing down more dramatic sections. 869