Whenever possible, you should avoid parsing the output of ls (see Greg's wiki on the subject). Basically, the output of ls will be ambiguous if there are funny characters in any of the filenames. It's also usually a waste of time. In this case, when you execute ls -d */, what happens is that the shell expands */ to a list of subdirectories (which is already exactly what you want), passes that list as arguments to ls -d, which looks at each one, says "yep, that's a directory all right" and prints it (in an inconsistent and sometimes ambiguous format). The ls command isn't doing anything useful!
Well, ok, it is doing one thing that's useful: if there are no subdirectories, */ will get left as is, ls will look for a subdirectory named "*", not find it, print an error message that it doesn't exist (to stderr), and not print the "*/" (to stdout).
The cleaner way to make an array of subdirectory names is to use the glob (*/) without passing it to ls. But in order to avoid putting "*/" in the array if there are no actual subdirectories, you should set nullglob first (again, see Greg's wiki):
shopt -s nullglob
array=(*/)
shopt -u nullglob # Turn off nullglob to make sure it doesn't interfere with anything later
echo "${array[@]}" # Note double-quotes to avoid extra parsing of funny characters in filenames
If you want to print an error message if there are no subdirectories, you're better off doing it yourself:
if (( ${#array[@]} == 0 )); then
echo "No subdirectories found" >&2
fi