Minor improvements.

1. Choosing a game in Titles Selection now checks if it is still installed in the Nintendo 3DS folder. If the game is not found, ask the user if (s)he would like to remove it from the cache. The [removed] game's save files are kept intact and left alone in the saves folder.
2. Streamlined some of the code by exchanging the fset command with fill command when generating dummy CIAs. Very minor speed bump when adding new titles to the cache.