Fix incremental crash on generic function appearing in nested position (#14148)

Fixes #14137 

Fix is trivial, I just forgot to call `super()` in one of my previous
PRs.

Author: ilevkivskyi

mypy/checkmember.py

@@ -806,6 +806,7 @@ class FreezeTypeVarsVisitor(TypeTraverserVisitor):
     def visit_callable_type(self, t: CallableType) -> None:
         for v in t.variables:
             v.id.meta_level = 0
+        super().visit_callable_type(t)
 
 
 def lookup_member_var_or_accessor(info: TypeInfo, name: str, is_lvalue: bool) -> SymbolNode | None:

test-data/unit/check-incremental.test

@@ -6334,3 +6334,17 @@ reveal_type(D().meth)
 [out2]
 tmp/m.py:4: note: Revealed type is "def [Self <: lib.C] (self: Self`0, other: Self`0) -> Self`0"
 tmp/m.py:5: note: Revealed type is "def (other: m.D) -> m.D"
+
+[case testIncrementalNestedGenericCallableCrash]
+from typing import TypeVar, Callable
+
+T = TypeVar("T")
+
+class B:
+    def foo(self) -> Callable[[T], T]: ...
+
+class C(B):
+    def __init__(self) -> None:
+        self.x = self.foo()
+[out]
+[out2]