Can't open local data files if non-directories exist in data/ dir
If a file exists in data/ then no data packages appear in the GUI.
The loop that iterates through directories in the local data/ dir needs to
distinguish files from directories so that files can be skipped instead of
breaking the loop.
#2 Updated by Will Tyburczy about 15 years ago
The most common way this seems to occur (unintentionally at least) is when Mac
users open the .morpho directory in Finder and then move or delete files in
data/ or its subdirectories. The OS creates ".DS_Store" files in these
directories. These files can safely be deleted if desired.