Removes empty when list all virtualenvs

Fixes #265

Author: robsonpeixoto

virtualenvwrapper.sh

@@ -578,6 +578,7 @@ function virtualenvwrapper_show_workon_options {
         | command \tr "\n" " " \
         | command \sed "s|/$VIRTUALENVWRAPPER_ENV_BIN_DIR/activate |/|g" \
         | command \tr "/" "\n" \
+        | command \sed "/^\s*$/d" \
         | (unset GREP_OPTIONS; command \egrep -v '^\*$') 2>/dev/null
 }