Fix books in subdirectories getting filtered

TODO

@@ -73,6 +73,8 @@ TODO
         ✓ Define every widget in code
     Bugs:
         Slider position change might be acting up
+        Deleted directories should be removed from the database
+        There are still slashes in the code
 
     Secondary:
         Annotations

lector/library.py

@@ -256,7 +256,7 @@ class Library:
                     if directory_name:
                         directory_name = directory_name.lower()
                     else:
-                        directory_name = path.rsplit('/')[-1].lower()
+                        directory_name = i.rsplit(os.sep)[-1].lower()
 
                     directory_tags = library_directories[i][1]
                     if directory_tags: