make a Value's address have type Value | None

Which is consistent with the GDB documentation:
https://sourceware.org/gdb/current/onlinedocs/gdb.html/Values-From-Inferior.html#Values-From-Inferior:~:text=Variable%3A%20Value%2Eaddress

Author: k4lizen

stubs/gdb/gdb/__init__.pyi

@@ -76,7 +76,7 @@ _ValueOrInt: TypeAlias = Value | int
 
 @disjoint_base
 class Value:
-    address: Value
+    address: Value | None
     is_optimized_out: bool
     type: Type
     dynamic_type: Type