ls: avoid invalid closedir() (#801)

* When temporarily enabling warnings.pm I observed a warning in DirEntries(): closedir() attempted on invalid dirhandle $dh
* The way the code was written, opendir() was always called even if the file was not a directory
* Delay the opendir() call until we know that we don't want to list a regular file
* opendir() should not happen if running "ls -d", or if the argument to DirEntries() is not a directory

bin/ls

@@ -150,9 +150,8 @@ sub DirEntries {
 	my @Entries = ();	# entries in original order
 	my $Name = "";		# entry name
 
-	if (!opendir($dh, $_[0]) || exists($Options{'d'})) {
+	if (exists $Options{'d'} || ! -d $_[0]) {
 		if (-e $_[0]) {
-			closedir($dh) if (defined($dh));
 			push(@Entries, $_[0]);
 			$Attributes{$_[0]} = stat($_[0]);
 			push(@Entries, \%Attributes);
@@ -161,6 +160,10 @@ sub DirEntries {
 		warn "$Program: can't access '$_[0]': $!\n";
 		return ();
 	}
+	unless (opendir $dh, $_[0]) {
+		warn "$Program: failed to open directory '$_[0]': $!\n";
+		return ();
+	}
 	while ($Name = readdir($dh)) {
 		next if (!exists($Options->{'a'}) &&
 		 $Name =~ m/^\./o);