How to turn empty spaces into "0" when converting .TXT file into a .CSV file?

I have joint angle data from a motion capture study. Sometimes there are gaps in the data for multiple reasons but it needs to read as "0" for propper analysis. Does anyone know a way to convert the .txt file to a csv file as well as turning the empty spaces into zeroes? I cannot get it to work when I try to use the "load" function and the "fopen" function but there is also a good chance I am doing it wrong. I have attached the raw data and what I would like line 1 to look like.

Any help is appreciated. Thank you!

[Scott MacKenzie]

Are you sure there are gaps? If I open your file in Excel using "tab" as the delimiter, the data are properly aligned in each column, with a label for each column, and without any missing data:

I think the gaps you are seeing are perhaps just an artefact of the tab delmiter. Check again.

[Thomas McCutcheon]

Actually, I think you are right. I was freaking out over nothing.