fix: something Shantanu found (#19859)

to be honest I have no idea what this code does, but I know we need to
fix it per advice from @hauntsaninja in #19846

Author: BobTheBuidler

mypy/strconv.py

@@ -388,7 +388,9 @@ def visit_name_expr(self, o: mypy.nodes.NameExpr) -> str:
             o.name, o.kind, o.fullname, o.is_inferred_def or o.is_special_form, o.node
         )
         if isinstance(o.node, mypy.nodes.Var) and o.node.is_final:
-            pretty += f" = {o.node.final_value}"
+            final_value = o.node.final_value
+            if final_value is not None:
+                pretty += f" = {o.node.final_value}"
         return short_type(o) + "(" + pretty + ")"
 
     def pretty_name(

test-data/unit/semanal-basic.test

@@ -521,7 +521,7 @@ MypyFile:1(
     NameExpr(True [builtins.True])
     Literal[True]?)
   AssignmentStmt:8(
-    NameExpr(n* [__main__.n] = None)
+    NameExpr(n* [__main__.n])
     CallExpr:8(
       NameExpr(func [__main__.func])
       Args())))