Fix dict.get issue for typeshed update (#18806)

Fix for issue uncovered in #18803

Author: cdce8p

mypy/partially_defined.py

@@ -45,7 +45,7 @@
 from mypy.patterns import AsPattern, StarredPattern
 from mypy.reachability import ALWAYS_TRUE, infer_pattern_value
 from mypy.traverser import ExtendedTraverserVisitor
-from mypy.types import Type, UninhabitedType
+from mypy.types import Type, UninhabitedType, get_proper_type
 
 
 class BranchState:
@@ -507,7 +507,8 @@ def visit_break_stmt(self, o: BreakStmt) -> None:
         self.tracker.skip_branch()
 
     def visit_expression_stmt(self, o: ExpressionStmt) -> None:
-        if isinstance(self.type_map.get(o.expr, None), (UninhabitedType, type(None))):
+        typ = self.type_map.get(o.expr)
+        if typ is None or isinstance(get_proper_type(typ), UninhabitedType):
             self.tracker.skip_branch()
         super().visit_expression_stmt(o)