fs/squashfs: sqfs_read: fix dangling pointer dirs->entry

dirs->entry shouldn't be left dangling as it could be freed twice.

Signed-off-by: Richard Genoud <richard.genoud@posteo.net>
diff --git a/fs/squashfs/sqfs.c b/fs/squashfs/sqfs.c
index f4cac3e..13e64be 100644
--- a/fs/squashfs/sqfs.c
+++ b/fs/squashfs/sqfs.c
@@ -1336,6 +1336,7 @@
 			break;
 
 		free(dirs->entry);
+		dirs->entry = NULL;
 	}
 
 	if (ret) {