When none of the directories exist, don't `find` within them.

nvm.sh

@@ -557,6 +557,7 @@ nvm_ls() {
     if [ -z "$PATTERN" ]; then
       PATTERN='v'
     fi
+    if [ -n "$NVM_DIRS_TO_SEARCH" ]; then
       VERSIONS="$(command find $NVM_DIRS_TO_SEARCH -maxdepth 1 -type d -name "$PATTERN*" \
         | command sed "s#$NVM_VERSION_DIR_IOJS/#"$NVM_IOJS_PREFIX"-#" \
         | command grep -v "$NVM_VERSION_DIR_IOJS" \
@@ -569,6 +570,7 @@ nvm_ls() {
         | command sort -s -t- -k1.1,1.1 \
         | command sed "s/^\($NVM_IOJS_PREFIX\)\./\1-/" \
         | command sed "s/^$NVM_NODE_PREFIX\.//")"
+    fi
 
     if [ $ZHS_HAS_SHWORDSPLIT_UNSET -eq 1 ] && nvm_has "unsetopt"; then
       unsetopt shwordsplit