backlight: Revamp error handling code to not leak the directory

To neatly free the directory pointer allocated by opendir(), adjust the error
handling paths to go through to the err label.

src/libbacklight.c

@@ -149,11 +149,11 @@ struct backlight *backlight_init(struct udev_device *drm_device,
 	char *pci_name = NULL;
 	char *chosen_path = NULL;
 	char *path = NULL;
-	DIR *backlights;
+	DIR *backlights = NULL;
 	struct dirent *entry;
 	enum backlight_type type = 0;
 	char buffer[100];
-	struct backlight *backlight;
+	struct backlight *backlight = NULL;
 	int ret;
 
 	if (!drm_device)
@@ -208,10 +208,10 @@ struct backlight *backlight_init(struct udev_device *drm_device,
 
 		if (asprintf(&backlight_path, "%s/%s", "/sys/class/backlight",
 			     entry->d_name) < 0)
-			return NULL;
+			goto err;
 
 		if (asprintf(&path, "%s/%s", backlight_path, "type") < 0)
-			return NULL;
+			goto err;
 
 		fd = open(path, O_RDONLY);
 
@@ -246,7 +246,7 @@ struct backlight *backlight_init(struct udev_device *drm_device,
 		free (path);
 
 		if (asprintf(&path, "%s/%s", backlight_path, "device") < 0)
-			return NULL;
+			goto err;
 
 		ret = readlink(path, buffer, sizeof(buffer) - 1);
 
@@ -280,7 +280,7 @@ struct backlight *backlight_init(struct udev_device *drm_device,
 	}
 
 	if (!chosen_path)
-		return NULL;
+		goto err;
 
 	backlight = malloc(sizeof(struct backlight));
 
@@ -298,10 +298,11 @@ struct backlight *backlight_init(struct udev_device *drm_device,
 	if (backlight->brightness < 0)
 		goto err;
 
+	closedir(backlights);
 	return backlight;
 err:
-	if (chosen_path)
-		free(chosen_path);
+	closedir(backlights);
+	free (chosen_path);
 	free (backlight);
 	return NULL;
 }