Metadata streaming: metadata list can include None. Re #155.

Mypy: not ideal, but some metadata stream list items can be None, possibly because Studio dies in the middle of retrieving metadata streaming values. Therefore metadata list function will return a list of None and integers.

addon/appModules/splstudio/splmisc.py

@@ -397,7 +397,7 @@ def cartExplorerRefresh(studioTitle: str, currentCarts: dict[str, Any]) -> dict[
 # Gather streaming flags into a list.
 # 18.04: raise runtime error if list is nothing
 # (thankfully the splbase's StudioAPI will return None if Studio handle is not found).
-def metadataList() -> list[int]:
+def metadataList() -> list[Optional[int]]:
 	metadata = [splbase.studioAPI(pos, 36) for pos in range(5)]
 	if metadata == [None, None, None, None, None]:
 		raise RuntimeError("Studio handle not found, no metadata list to return")