ast: fix (*ast.File).End check shadow no entry

[visualfc]

fix (*ast.File).End bad result if classfile add shadow func Classfname.

example get.yap ast.File.End return last shadow func Classfname.End()

[codecov[bot]]

Codecov Report

All modified and coverable lines are covered by tests :white_check_mark:

Project coverage is 93.27%. Comparing base (f3b7a43) to head (da59ab6).

Additional details and impacted files

```diff @@ Coverage Diff @@ ## main #1860 +/- ## ======================================= Coverage 93.27% 93.27% ======================================= Files 40 40 Lines 11597 11597 ======================================= Hits 10817 10817 Misses 623 623 Partials 157 157 ```

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