fix: remove unnecessary None checks

Author: vberlier

beet/library/base.py

@@ -535,8 +535,6 @@ def list_files(
             extend = origin
 
         for path, item in self.extra.items():
-            if item is None:
-                continue
             if extensions and not any(path.endswith(ext) for ext in extensions):
                 continue
             if extend and not isinstance(item, extend):
@@ -1029,8 +1027,6 @@ def list_files(
             extend = origin
 
         for path, item in self.extra.items():
-            if item is None:
-                continue
             if extensions and not any(path.endswith(ext) for ext in extensions):
                 continue
             if extend and not isinstance(item, extend):
@@ -1163,7 +1159,7 @@ def unveil(self, prefix: str, origin: Union[FileSystemPath, UnveilMapping]):
 
     def dump(self, origin: FileOrigin):
         """Write the content of the pack to a zipfile or to the filesystem"""
-        extra = {path: item for path, item in self.extra.items() if item is not None}
+        extra = {path: item for path, item in self.extra.items()}
         _dump_files(origin, extra)
 
         for namespace_name, namespace in self.items():